Sampling procedures for inspection by attributes -- Part 3: Skip-lot sampling procedures

This part of ISO 2859 specifies generic  skip-lot sampling procedures for  acceptance inspection by attributes. The  purpose of these procedures is to provide a  way of reducing the inspection effort on  products of high quality submitted by a  supplier who has a satisfactory quality  assurance system and effective quality  controls. The reduction in inspection effort  is achieved by determining at random, with  a specified probability, whether a lot  presented for inspection will be accepted  without inspection. This procedure extends  the principle of the random selection of  sample items already applied in ISO 2859-1  to the random selection of lots. The skip-lot  sampling procedures specified in this part of  ISO 2859 are applicable to, but not limited  to, inspection of a) end items, such as  complete products or sub-assemblies, b)  components and raw materials, and c)  materials in process.

Règles d'échantillonnage pour les contrôles par attributs -- Partie 3: Procédures d'échantillonnage successif partiel

L'ISO 2859-3 spécifie des procédures génériques d'échantillonnage successif partiel destinées à un contrôle par attributs pour acceptation. L'objectif de ces procédures est de fournir un moyen de réduire les efforts de contrôle sur des produits de haute qualité présentés par un fournisseur disposant d'un système d'assurance de la qualité satisfaisant et de contrôles de la qualité efficaces. La réduction des efforts de contrôle est obtenue en déterminant de manière aléatoire, avec une probabilité spécifiée, si un lot présenté au contrôle sera accepté sans contrôle. Cette procédure élargit le principe de sélection aléatoire d'individus d'échantillonnage, déjà appliqué dans l'ISO 2859-1, à la sélection aléatoire de lots.
Les procédures d'échantillonnage successif partiel spécifiées dans l'ISO 2859-3:2005 sont applicables, mais d'une manière non limitative, aux contrôles de produits finis tels que des produits ou sous-ensembles complets, aux contrôles de composants et de matières premières, et aux contrôles de matériaux en cours de fabrication.

Postopki vzorčenja za kontrolo po opisnih spremenljivkah – 3. del: Postopki vzorčenja z izpuščanjem partij

General Information

Status
Published
Publication Date
31-Mar-2006
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
01-Apr-2006
Due Date
01-Apr-2006
Completion Date
01-Apr-2006

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INTERNATIONAL ISO
STANDARD 2859-3
Second edition
2005-05-01
Sampling procedures for inspection by
attributes —
Part 3:
Skip-lot sampling procedures
Règles d'échantillonnage pour les contrôles par attributs —
Partie 3: Procédures d’échantillonnage successif partiel
Reference number
ISO 2859-3:2005(E)
ISO 2005
---------------------- Page: 1 ----------------------
ISO 2859-3:2005(E)
PDF disclaimer

This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but

shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In

downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat

accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.

Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation

parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In

the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.

© ISO 2005

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,

electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or

ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2005 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 2859-3:2005(E)
Contents Page

Foreword............................................................................................................................................................ iv

1 Scope...................................................................................................................................................... 1

2 Normative references ........................................................................................................................... 1

3 Terms, definitions and symbols .......................................................................................................... 1

3.1 Terms and definitions........................................................................................................................... 1

3.2 Symbols and abbreviated terms.......................................................................................................... 3

4 General requirements ........................................................................................................................... 3

5 Supplier and product qualification...................................................................................................... 4

5.1 Supplier qualification............................................................................................................................ 4

5.2 Product qualification ............................................................................................................................ 5

5.3 Qualification score................................................................................................................................ 6

5.4 Example for product qualification....................................................................................................... 8

6 Skip-lot sampling procedures ............................................................................................................. 9

6.1 General................................................................................................................................................... 9

6.2 Initial inspection frequency and its determination.......................................................................... 11

6.3 Inspection frequency and shifting .................................................................................................... 11

6.4 Sampling plans, lot selection and inspection procedures (States 2 and 3) ................................. 14

6.5 Skip-lot interruption............................................................................................................................ 15

6.6 Requalification .................................................................................................................................... 16

6.7 Product disqualification ..................................................................................................................... 16

6.8 Supplier disqualification and suspension........................................................................................17

7 Supplier responsibilities .................................................................................................................... 17

8 Inspection agency and responsible authority responsibilities...................................................... 18

8.1 General................................................................................................................................................. 18

8.2 Responsibilities on supplier qualification........................................................................................ 19

8.3 Other responsibilities ......................................................................................................................... 19

9 Compatibility with ISO 2859-1............................................................................................................ 20

9.1 Limitations ........................................................................................................................................... 20

9.2 Relation to reduced inspection ......................................................................................................... 20

10 Additional information........................................................................................................................ 21

10.1 Design basis ........................................................................................................................................ 21

10.2 Statistical characteristics of the skip-lot procedures ..................................................................... 21

Annex A (normative) Optional requirements to be agreed prior to product qualification........................ 23

Annex B (normative) Procedures for random selection at specified inspection frequency .................... 25

Annex C (informative) Factors used in deciding between skip-lot inspection and reduced

inspection ............................................................................................................................................ 27

Bibliography ..................................................................................................................................................... 29

© ISO 2005 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 2859-3:2005(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies

(ISO member bodies). The work of preparing International Standards is normally carried out through ISO

technical committees. Each member body interested in a subject for which a technical committee has been

established has the right to be represented on that committee. International organizations, governmental and

non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the

International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International Standards

adopted by the technical committees are circulated to the member bodies for voting. Publication as an

International Standard requires approval by at least 75 % of the member bodies casting a vote.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent

rights. ISO shall not be held responsible for identifying any or all such patent rights.

ISO 2859-3 was prepared by Technical Committee ISO/TC 69, Applications of statistical methods,

Subcommittee SC 5, Acceptance sampling.

This second edition cancels and replaces the first edition (ISO 2859-3:1991), which has been technically

revised.

ISO 2859 consists of the following parts, under the general title Sampling procedures for inspection by

attributes:

 Part 1: Sampling schemes indexed by acceptance quality limit (AQL) for lot-by-lot inspection

 Part 2: Sampling plans indexed by limiting quality (LQ) for isolated lot inspection

 Part 3: Skip-lot sampling procedures
 Part 4: Procedures for assessment of declared quality levels

 Part 5: System of sequential sampling plans indexed by acceptance quality limit (AQL) for lot-by-lot

inspection.
 Part 10: Overview of the ISO 2859 attribute sampling systems
iv © ISO 2005 – All rights reserved
---------------------- Page: 4 ----------------------
INTERNATIONAL STANDARD ISO 2859-3:2005(E)
Sampling procedures for inspection by attributes —
Part 3:
Skip-lot sampling procedures
1 Scope

This part of ISO 2859 specifies generic skip-lot sampling procedures for acceptance inspection by attributes.

The purpose of these procedures is to provide a way of reducing the inspection effort on products of high

quality submitted by a supplier who has a satisfactory quality assurance system and effective quality controls.

The reduction in inspection effort is achieved by determining at random, with a specified probability, whether a

lot presented for inspection will be accepted without inspection. This procedure extends the principle of the

random selection of sample items already applied in ISO 2859-1 to the random selection of lots.

The skip-lot sampling procedures specified in this part of ISO 2859 are applicable to, but not limited to,

inspection of
a) end items, such as complete products or sub-assemblies,
b) components and raw materials, and
c) materials in process.
2 Normative references

The following referenced documents are indispensable for the application of this document. For dated

references, only the edition cited applies. For undated references, the latest edition of the referenced

document (including any amendments) applies.

ISO 2859-1:1999, Sampling procedures for inspection by attributes — Part 1:Sampling schemes indexed by

acceptance quality limit (AQL) for lot-by-lot inspection

ISO 3534-1, Statistics — Vocabulary and symbols — Part 1: Probability and general statistical terms

ISO 3534-2, Statistics — Vocabulary and symbols — Part 2: Applied statistics
3 Terms, definitions and symbols
3.1 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 2859-1, ISO 3534-1, ISO 3534-2

and the following apply. For ease of reference, some terms are quoted from these standards.

3.1.1
continuous production
production that is at a steady rate

NOTE Production is considered continuous if the production has been continued for a specified production period at

a specified production frequency (see 5.2.1). Continuous production is considered a stabilizing factor of the manufacturing

or assembly processes.
© ISO 2005 – All rights reserved 1
---------------------- Page: 5 ----------------------
ISO 2859-3:2005(E)
3.1.2
disqualification
failure to qualify for skip-lot sampling inspection (3.1.11)
3.1.3
inspection agency

independent third party with the responsibility for lot inspection and qualification assessment

3.1.4
inspection frequency
probability that a lot is inspected

NOTE Inspection frequencies specified in this part of ISO 2859 are 1/2,1/3,1/4 and 1/5.

3.1.5
interruption

cessation of skip-lot sampling inspection (3.1.11), ending with a return either to skip-lot sampling inspection or

to lot-by-lot inspection
3.1.6
lot-by-lot inspection
inspection of products submitted in a series of lots

NOTE 1 In this part of ISO 2859, a sample (or samples) is (are) drawn from each lot and inspected using acceptance

sampling procedures by attributes given in ISO 2859-1.

NOTE 2 In this part of ISO 2859, lot-by-lot inspection is used both in State 1 (qualification period) and State 3 (skip-lot

interruption state) (see 5.1).
3.1.7
product qualification

assessment of the product to determine its suitability for skip-lot sampling inspection (3.1.11)

3.1.8
qualification score

running total derived according to given rules from the immediately preceding quality history, and used in

making decisions regarding qualification, changes in inspection frequency (3.1.4), interruption (3.1.5),

disqualification (3.1.2) and requalification (3.1.9)
3.1.9
requalification
qualification for a resumption of skip-lot sampling inspection (3.1.11)
3.1.10
responsible authority

person or group of people who has responsibility and authority to manage inspection systems appropriately

NOTE In this part of ISO 2859, the responsible authority has responsibility and authority to assess and verify supplier

qualification, decide various criteria and judge switch inspection stages.
3.1.11
skip-lot sampling inspection

sampling inspection procedure in which some lots in a series are accepted without inspection when the

sampling results for a stated number of immediately preceding lots meet stated criteria

NOTE The lots to be inspected are chosen randomly in accordance with a stated (skip-lot) inspection frequency. An

inspection frequency of 1 in 2, for example, means that the long run average proportion of lots inspected is 1/2.

2 © ISO 2005 – All rights reserved
---------------------- Page: 6 ----------------------
ISO 2859-3:2005(E)
3.1.12
supplier qualification

assessment of the supplier’s competence to implement skip-lot sampling inspection (3.1.11)

3.2 Symbols and abbreviated terms
The symbols and abbreviated terms used in this document are as follows:
Ac acceptance number;
Ac acceptance number for the corresponding single sampling plan;
Ac first acceptance number (for the double or multiple sampling plan);
Ac second acceptance number (for the double or multiple sampling plan);
d number of nonconforming items or nonconformities in the sample;

k number of lots used for inspection frequency (the inspection frequency is 1 in k; i.e. 1/k);

n sample size.
4 General requirements

4.1 Skip-lot inspection may only be used when both the supplier and the product are qualified. The

requirements for qualification are specified in Clause 5.

NOTE The skip-lot sampling procedures specified in this part of ISO 2859 should be distinguished from Dodge’s

skip-lot sampling plans. See [1], [2] and [3] in the Bibliography.

4.2 This part of ISO 2859 is intended to supplement the ISO 2859-1 sampling system, and may be used

together with ISO 2859-1. Unless otherwise specified in this part of ISO 2859, the provisions of ISO 2859-1

shall apply. ISO 2859-10 provides useful information concerning the use of the standards in the ISO 2859

series.

4.3 The skip-lot sampling procedures specified in this part of ISO 2859 are intended only for a continuing

series of lots and shall not be used for isolated lots. All lots in the series are expected to be of a similar quality

and there should be reason to believe that lots not inspected are of the same quality as the ones inspected.

4.4 Skip-lot sampling may be used instead of reduced inspection if it is more cost effective to do so (see 9.2

and Annex C), but its application and switching rules are different from those of reduced inspection in

ISO 2859-1.

4.5 There are some limitations to the use of skip-lot sampling procedures (see 9.1).

4.6 When different acceptance quality limit (AQL) values are specified for two or more classes of

nonconforming items or nonconformities, special care should be taken to ensure correct application of the

standard (see 5.2.2 to 6.6 and 10.2).

4.7 Inspection may take place at the supplier’s or purchaser’s locations, or at an interface between

operations of a production process.

4.8 As every product has its own environment and characteristics, options are provided so that the supplier

and the responsible authority may select the appropriate options to meet the specifics of the product and its

environment. All choices as a result of this tailoring should be specified in a written document.

4.9 When specified by the purchaser, this part of ISO 2859 may be referenced in a purchasing or

specification contract, inspection instruction, or other contractual documents.
© ISO 2005 – All rights reserved 3
---------------------- Page: 7 ----------------------
ISO 2859-3:2005(E)

4.10 The responsible authority and the inspection agency are to be designated in one of the above

documents. This part of ISO 2859 assumes that both lot inspection and qualification assessment are

conducted by an inspection agency, being an independent third party. However, the purchaser may conduct

both. It is necessary to replace the term “inspection agency” by “purchaser’s inspector” or “assessing team” as

occasion demands (see 5.1.2, 5.2.3 and Clauses 7 and 8).
5 Supplier and product qualification
5.1 Supplier qualification
5.1.1 Requirements for supplier qualification
The requirements for supplier qualification are as follows.

a) The supplier shall have implemented and maintained a documented system for controlling product quality

and design changes. It is assumed that the system includes inspection by the supplier of each lot

produced and the recording of inspection results.

b) The supplier shall have instituted a system that is capable of detecting and correcting shifts in quality

levels and monitoring process changes that may adversely affect quality. The supplier’s personnel

responsible for the application of the system shall demonstrate a clear understanding of the applicable

standards, systems and procedures to be followed.

c) The supplier shall not have experienced any change that might adversely affect quality.

5.1.2 Assessment for supplier qualification

An assessment team may be dispatched for the assessment for supplier qualification. When the assessment

is conducted by the inspection agency, a typical example of what is to be examined and how functions and

responsibilities are shared is shown in Clause 8.

When the purchaser conducts the assessment for supplier qualification, the functions and responsibilities of

the assessment team are similar to those of the inspection agency.

If the supplier has been qualified for another similar product, the responsible authority may consider this fact in

determining the degree of additional assessment for supplier qualification.

The responsible authority shall determine whether the supplier is eligible for skip-lot inspection after reviewing

the assessment results (see 8.2).

Assessment and registration of the supplier in accordance with the third-party assessment standards given in

ISO 9001 for the group of products containing the product concerned should be considered in determining

eligibility for skip-lot inspection.
5.1.3 Verification of supplier qualification

Supplier qualification shall be verified at a frequency agreed to by both the supplier and the responsible

authority. The purpose of this verification is to determine whether or not the supplier is still able to understand

and follow the quality control procedures.

The method of verification is similar to the method of assessment, but it may be simplified so that the review

may be conducted by an inspector in place of an assessment team (see 8.2).
4 © ISO 2005 – All rights reserved
---------------------- Page: 8 ----------------------
ISO 2859-3:2005(E)
5.2 Product qualification
5.2.1 Generic requirements for product qualification
Generic requirements for the product qualification are as follows.
a) The product shall be of stable design.

b) The product shall not have any critical classes of nonconforming items or nonconformities.

c) The specified AQL(s) shall be at least 0,025 %. The specified inspection level(s) shall be general

inspection levels I, II or III (see ISO 2859-1).

d) The product shall have been on normal or reduced inspection or a combination of normal and reduced

inspection (see ISO 2859-1) during the qualification period. A product that has been on tightened

inspection at any time during the qualification period is ineligible for skip-lot inspection.

e) The product shall have been produced on an essentially continuous basis for a specified production

period at a specified production frequency.

Both the minimum production period and the minimum production frequency should be specified, based

on the agreement between the supplier and the responsible authority (see Annex A).

If no minimum production period is specified, the period shall be 6 months. Whenever production is held

pending sample approval, only the time period after approval and resumption of production shall be

included.

If no minimum production frequency is specified, the minimum production frequency shall be once per

month, or at least one lot shall be submitted each month.

Products of a similar nature shipped to other parties may be considered in the determination of

“essentially continuous”, if agreed to by both the supplier and the responsible authority.

f) The product quality shall have been maintained at the AQL or better (see ISO 2859-1) for a period of

stability mutually agreed to by both the supplier and the responsible authority. If no period is specified, the

period shall be 6 months.
5.2.2 Specific requirements for product qualification

5.2.2.1 The specific requirements for the product qualification are that the following criteria shall be met:

a) the preceding 10 or more consecutive lots have been accepted on original inspection; the term “on

original inspection” means that the results of resubmitted lots shall not be included;

b) the qualification score (see 5.3) reaches or exceeds 50 within 20 consecutive lots; if the qualification

period exceeds 20 lots, use the qualification score recalculated for the last 20 lots.

5.2.2.2 There are the following limitations on applicable sampling plans:

a) fractional acceptance number sampling plans (see ISO 2859-1:1999, Clause 13) shall not be used;

b) multiple sampling plans are permitted only when the first acceptance number is a numerical value.

5.2.3 Assessment for product qualification

An assessment for product qualification shall not be made prior to the assessment for supplier qualification,

although both assessments may be made at the same time.

The product qualification assessment shall be conducted by an assessment team, an inspector or an

inspection agency. When the assessment is conducted by an inspection agency, a typical example of what is

to be examined and how functions and responsibilities may be shared is shown in Clause 8 and Annex A.

© ISO 2005 – All rights reserved 5
---------------------- Page: 9 ----------------------
ISO 2859-3:2005(E)

When the assessment for product qualification is conducted by the purchaser the functions and

responsibilities of the assessment team or the inspector are similar to those of the inspection agency. The

responsible authority shall determine whether the product is eligible for skip-lot inspection after reviewing the

assessment results (see 8.3). Product qualification assessments should always be performed, even in the

case of a supplier with a quality management system certified to be in conformity with ISO 9001.

5.2.4 Verification of product qualification

Product qualification shall be verified at a frequency agreed to by both the supplier and the responsible

authority. The purpose of this verification is to determine whether or not the quality control procedures for the

product continue to be followed. The verification should be made together with the verification for supplier

qualification.

The method of verification is similar to the method of assessment, but it may be simplified (see 8.3).

5.3 Qualification score
5.3.1 General

The qualification score is used not only for qualification, but also for making decisions regarding a change in

frequency, interruption of the procedure, requalification and disqualification. The rules given shall be applied in

the same manner to each state.

In the case of inspection for nonconformities per 100 items, the term “nonconforming item” in the following

rules shall be replaced by “nonconformity”.
5.3.2 Single sampling plans for normal inspection

The rules for calculating the qualification score for normal inspection single sampling plans are as follows:

a) Sampling plans with Ac W 3:

 if the lot would have been accepted had the AQL been two steps tighter, add 5 to the qualification

score;

 if the lot would have been accepted had the AQL been one step but not two steps tighter, add 3 to

the qualification score;
 otherwise reset the qualification score to zero.
b) Sampling plan with Ac = 2:

 if the lot is accepted with no nonconforming item in the sample, add 5 to the qualification score;

 if the lot is accepted with one nonconforming item in the sample, add 3 to the qualification score;

 otherwise reset the qualification score to zero.
c) Sampling plan with Ac = 1:

 if the lot is accepted with no nonconforming item in the sample, add 5 to the qualification score;

 if the lot is accepted with one nonconforming item in the sample, add 1 to the qualification score;

 otherwise reset the qualification score to zero.
d) Sampling plan with Ac = 0:
 if the lot is accepted, add 3 to the qualification score;
 otherwise reset the qualification score to zero.
6 © ISO 2005 – All rights reserved
---------------------- Page: 10 ----------------------
ISO 2859-3:2005(E)
5.3.3 Double sampling plans for normal inspection

The rules for calculating the qualification score for normal inspection double sampling plans are as follows:

a) Sampling plans with Ac W 1:

 if the lot would have been accepted after the first sample if the AQL had been one step tighter, add 5

to the qualification score;

 if the lot is accepted after the first sample but would not have been accepted if the AQL had been

one step tighter, add 3 to the qualification score;
 otherwise reset the qualification score to zero.
b) Sampling plan with Ac = 0, Ac = 1 or 3 [Ac = 1 or 2]:
1 2 0

 if the lot is accepted with no nonconforming item in the sample, add 5 to the qualification score;

 if the lot is accepted with one nonconforming item in the cumulative sample, add 1 to the qualification

score;
 otherwise reset the qualification score to zero.
5.3.4 Multiple sampling plans for normal inspection

The rules for calculating the qualification score for normal inspection multiple sampling plans are as follows:

 if the lot is accepted after the first sample, add 5 to the qualification score;

 if the lot is accepted after the second or the third sample, add 3 to the qualification score;

 otherwise reset the qualification score to zero.
Multiple sampling plans are permitted only when Ac W 0.
5.3.5 Sampling plans for reduced inspection

5.3.5.1 For all the single, double and multiple sampling plans for reduced inspection, the rules for the

corresponding normal inspection shall apply, except for the following changes to the values to be added to the

qualification score:
 5 for normal inspection shall be replaced by 3 for reduced inspection;
 3 for normal inspection shall be replaced by 1 for reduced inspection.

5.3.5.2 For example, the rules for reduced inspection single sampling plans with Ac ==== 3 are as follows:

 if the lot would have been accepted had the AQL been two steps tighter, add 3 to the qualification score;

 if the lot would have been accepted had the AQL been one step but not two steps tighter, add 1 to the

qualification score;
 otherwise reset the qualification score to zero.

NOTE Under reduced inspection, 17 or more lots are necessary for qualification. For reduced inspection single

sampling plans with Ac = 0, the qualification score addition is 1 per lot, and will never reach 50 within 20 lots [see 5.2.2 b)].

© ISO 2005 – All rights reserved 7
---------------------- Page: 11 ----------------------
ISO 2859-3:2005(E)
5.3.6 Resetting of the qualification score
If any of the following occurs, reset the qualification score to zero:
 any switching except for the switching from normal to reduced inspection;
 any state change (qualification, requalification or disqualification);
 any frequency shift.
5.4 Example for product qualification
The following is a numerical example for product qualification.

Example 1: In a product qualification period, normal or reduced inspection or a combination of normal and

reduced inspection of ISO 2859-1 is applied [see 5.2.1 d)]. Suppose that a qualified manufacturer produces

capacitors that satisfy the general requirements of 5.2.1 a) to d). In addition, assume the following:

 the requirements of an essentially continuous production have been satisfied [see 5.2.1 e)];

 the specified AQL is 0,65 % nonconforming;
 the agreed period of stability is 4 months [see 5.2.
...

SLOVENSKI STANDARD
SIST ISO 2859-3:2006
01-april-2006
Postopki vzorčenja za kontrolo po opisnih spremenljivkah – 3. del: Postopki
vzorčenja z izpuščanjem partij

Sampling procedures for inspection by attributes -- Part 3: Skip-lot sampling procedures

Règles d'échantillonnage pour les contrôles par attributs -- Partie 3: Procédures

d'échantillonnage successif partiel
Ta slovenski standard je istoveten z: ISO 2859-3:2005
ICS:
03.120.30 Uporaba statističnih metod Application of statistical
methods
SIST ISO 2859-3:2006 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST ISO 2859-3:2006
---------------------- Page: 2 ----------------------
SIST ISO 2859-3:2006
INTERNATIONAL ISO
STANDARD 2859-3
Second edition
2005-05-01
Sampling procedures for inspection by
attributes —
Part 3:
Skip-lot sampling procedures
Règles d'échantillonnage pour les contrôles par attributs —
Partie 3: Procédures d’échantillonnage successif partiel
Reference number
ISO 2859-3:2005(E)
ISO 2005
---------------------- Page: 3 ----------------------
SIST ISO 2859-3:2006
ISO 2859-3:2005(E)
PDF disclaimer

This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but

shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In

downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat

accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.

Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation

parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In

the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.

© ISO 2005

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,

electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or

ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2005 – All rights reserved
---------------------- Page: 4 ----------------------
SIST ISO 2859-3:2006
ISO 2859-3:2005(E)
Contents Page

Foreword............................................................................................................................................................ iv

1 Scope...................................................................................................................................................... 1

2 Normative references ........................................................................................................................... 1

3 Terms, definitions and symbols .......................................................................................................... 1

3.1 Terms and definitions........................................................................................................................... 1

3.2 Symbols and abbreviated terms.......................................................................................................... 3

4 General requirements ........................................................................................................................... 3

5 Supplier and product qualification...................................................................................................... 4

5.1 Supplier qualification............................................................................................................................ 4

5.2 Product qualification ............................................................................................................................ 5

5.3 Qualification score................................................................................................................................ 6

5.4 Example for product qualification....................................................................................................... 8

6 Skip-lot sampling procedures ............................................................................................................. 9

6.1 General................................................................................................................................................... 9

6.2 Initial inspection frequency and its determination.......................................................................... 11

6.3 Inspection frequency and shifting .................................................................................................... 11

6.4 Sampling plans, lot selection and inspection procedures (States 2 and 3) ................................. 14

6.5 Skip-lot interruption............................................................................................................................ 15

6.6 Requalification .................................................................................................................................... 16

6.7 Product disqualification ..................................................................................................................... 16

6.8 Supplier disqualification and suspension........................................................................................17

7 Supplier responsibilities .................................................................................................................... 17

8 Inspection agency and responsible authority responsibilities...................................................... 18

8.1 General................................................................................................................................................. 18

8.2 Responsibilities on supplier qualification........................................................................................ 19

8.3 Other responsibilities ......................................................................................................................... 19

9 Compatibility with ISO 2859-1............................................................................................................ 20

9.1 Limitations ........................................................................................................................................... 20

9.2 Relation to reduced inspection ......................................................................................................... 20

10 Additional information........................................................................................................................ 21

10.1 Design basis ........................................................................................................................................ 21

10.2 Statistical characteristics of the skip-lot procedures ..................................................................... 21

Annex A (normative) Optional requirements to be agreed prior to product qualification........................ 23

Annex B (normative) Procedures for random selection at specified inspection frequency .................... 25

Annex C (informative) Factors used in deciding between skip-lot inspection and reduced

inspection ............................................................................................................................................ 27

Bibliography ..................................................................................................................................................... 29

© ISO 2005 – All rights reserved iii
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SIST ISO 2859-3:2006
ISO 2859-3:2005(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies

(ISO member bodies). The work of preparing International Standards is normally carried out through ISO

technical committees. Each member body interested in a subject for which a technical committee has been

established has the right to be represented on that committee. International organizations, governmental and

non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the

International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International Standards

adopted by the technical committees are circulated to the member bodies for voting. Publication as an

International Standard requires approval by at least 75 % of the member bodies casting a vote.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent

rights. ISO shall not be held responsible for identifying any or all such patent rights.

ISO 2859-3 was prepared by Technical Committee ISO/TC 69, Applications of statistical methods,

Subcommittee SC 5, Acceptance sampling.

This second edition cancels and replaces the first edition (ISO 2859-3:1991), which has been technically

revised.

ISO 2859 consists of the following parts, under the general title Sampling procedures for inspection by

attributes:

 Part 1: Sampling schemes indexed by acceptance quality limit (AQL) for lot-by-lot inspection

 Part 2: Sampling plans indexed by limiting quality (LQ) for isolated lot inspection

 Part 3: Skip-lot sampling procedures
 Part 4: Procedures for assessment of declared quality levels

 Part 5: System of sequential sampling plans indexed by acceptance quality limit (AQL) for lot-by-lot

inspection.
 Part 10: Overview of the ISO 2859 attribute sampling systems
iv © ISO 2005 – All rights reserved
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SIST ISO 2859-3:2006
INTERNATIONAL STANDARD ISO 2859-3:2005(E)
Sampling procedures for inspection by attributes —
Part 3:
Skip-lot sampling procedures
1 Scope

This part of ISO 2859 specifies generic skip-lot sampling procedures for acceptance inspection by attributes.

The purpose of these procedures is to provide a way of reducing the inspection effort on products of high

quality submitted by a supplier who has a satisfactory quality assurance system and effective quality controls.

The reduction in inspection effort is achieved by determining at random, with a specified probability, whether a

lot presented for inspection will be accepted without inspection. This procedure extends the principle of the

random selection of sample items already applied in ISO 2859-1 to the random selection of lots.

The skip-lot sampling procedures specified in this part of ISO 2859 are applicable to, but not limited to,

inspection of
a) end items, such as complete products or sub-assemblies,
b) components and raw materials, and
c) materials in process.
2 Normative references

The following referenced documents are indispensable for the application of this document. For dated

references, only the edition cited applies. For undated references, the latest edition of the referenced

document (including any amendments) applies.

ISO 2859-1:1999, Sampling procedures for inspection by attributes — Part 1:Sampling schemes indexed by

acceptance quality limit (AQL) for lot-by-lot inspection

ISO 3534-1, Statistics — Vocabulary and symbols — Part 1: Probability and general statistical terms

ISO 3534-2, Statistics — Vocabulary and symbols — Part 2: Applied statistics
3 Terms, definitions and symbols
3.1 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 2859-1, ISO 3534-1, ISO 3534-2

and the following apply. For ease of reference, some terms are quoted from these standards.

3.1.1
continuous production
production that is at a steady rate

NOTE Production is considered continuous if the production has been continued for a specified production period at

a specified production frequency (see 5.2.1). Continuous production is considered a stabilizing factor of the manufacturing

or assembly processes.
© ISO 2005 – All rights reserved 1
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SIST ISO 2859-3:2006
ISO 2859-3:2005(E)
3.1.2
disqualification
failure to qualify for skip-lot sampling inspection (3.1.11)
3.1.3
inspection agency

independent third party with the responsibility for lot inspection and qualification assessment

3.1.4
inspection frequency
probability that a lot is inspected

NOTE Inspection frequencies specified in this part of ISO 2859 are 1/2,1/3,1/4 and 1/5.

3.1.5
interruption

cessation of skip-lot sampling inspection (3.1.11), ending with a return either to skip-lot sampling inspection or

to lot-by-lot inspection
3.1.6
lot-by-lot inspection
inspection of products submitted in a series of lots

NOTE 1 In this part of ISO 2859, a sample (or samples) is (are) drawn from each lot and inspected using acceptance

sampling procedures by attributes given in ISO 2859-1.

NOTE 2 In this part of ISO 2859, lot-by-lot inspection is used both in State 1 (qualification period) and State 3 (skip-lot

interruption state) (see 5.1).
3.1.7
product qualification

assessment of the product to determine its suitability for skip-lot sampling inspection (3.1.11)

3.1.8
qualification score

running total derived according to given rules from the immediately preceding quality history, and used in

making decisions regarding qualification, changes in inspection frequency (3.1.4), interruption (3.1.5),

disqualification (3.1.2) and requalification (3.1.9)
3.1.9
requalification
qualification for a resumption of skip-lot sampling inspection (3.1.11)
3.1.10
responsible authority

person or group of people who has responsibility and authority to manage inspection systems appropriately

NOTE In this part of ISO 2859, the responsible authority has responsibility and authority to assess and verify supplier

qualification, decide various criteria and judge switch inspection stages.
3.1.11
skip-lot sampling inspection

sampling inspection procedure in which some lots in a series are accepted without inspection when the

sampling results for a stated number of immediately preceding lots meet stated criteria

NOTE The lots to be inspected are chosen randomly in accordance with a stated (skip-lot) inspection frequency. An

inspection frequency of 1 in 2, for example, means that the long run average proportion of lots inspected is 1/2.

2 © ISO 2005 – All rights reserved
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SIST ISO 2859-3:2006
ISO 2859-3:2005(E)
3.1.12
supplier qualification

assessment of the supplier’s competence to implement skip-lot sampling inspection (3.1.11)

3.2 Symbols and abbreviated terms
The symbols and abbreviated terms used in this document are as follows:
Ac acceptance number;
Ac acceptance number for the corresponding single sampling plan;
Ac first acceptance number (for the double or multiple sampling plan);
Ac second acceptance number (for the double or multiple sampling plan);
d number of nonconforming items or nonconformities in the sample;

k number of lots used for inspection frequency (the inspection frequency is 1 in k; i.e. 1/k);

n sample size.
4 General requirements

4.1 Skip-lot inspection may only be used when both the supplier and the product are qualified. The

requirements for qualification are specified in Clause 5.

NOTE The skip-lot sampling procedures specified in this part of ISO 2859 should be distinguished from Dodge’s

skip-lot sampling plans. See [1], [2] and [3] in the Bibliography.

4.2 This part of ISO 2859 is intended to supplement the ISO 2859-1 sampling system, and may be used

together with ISO 2859-1. Unless otherwise specified in this part of ISO 2859, the provisions of ISO 2859-1

shall apply. ISO 2859-10 provides useful information concerning the use of the standards in the ISO 2859

series.

4.3 The skip-lot sampling procedures specified in this part of ISO 2859 are intended only for a continuing

series of lots and shall not be used for isolated lots. All lots in the series are expected to be of a similar quality

and there should be reason to believe that lots not inspected are of the same quality as the ones inspected.

4.4 Skip-lot sampling may be used instead of reduced inspection if it is more cost effective to do so (see 9.2

and Annex C), but its application and switching rules are different from those of reduced inspection in

ISO 2859-1.

4.5 There are some limitations to the use of skip-lot sampling procedures (see 9.1).

4.6 When different acceptance quality limit (AQL) values are specified for two or more classes of

nonconforming items or nonconformities, special care should be taken to ensure correct application of the

standard (see 5.2.2 to 6.6 and 10.2).

4.7 Inspection may take place at the supplier’s or purchaser’s locations, or at an interface between

operations of a production process.

4.8 As every product has its own environment and characteristics, options are provided so that the supplier

and the responsible authority may select the appropriate options to meet the specifics of the product and its

environment. All choices as a result of this tailoring should be specified in a written document.

4.9 When specified by the purchaser, this part of ISO 2859 may be referenced in a purchasing or

specification contract, inspection instruction, or other contractual documents.
© ISO 2005 – All rights reserved 3
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SIST ISO 2859-3:2006
ISO 2859-3:2005(E)

4.10 The responsible authority and the inspection agency are to be designated in one of the above

documents. This part of ISO 2859 assumes that both lot inspection and qualification assessment are

conducted by an inspection agency, being an independent third party. However, the purchaser may conduct

both. It is necessary to replace the term “inspection agency” by “purchaser’s inspector” or “assessing team” as

occasion demands (see 5.1.2, 5.2.3 and Clauses 7 and 8).
5 Supplier and product qualification
5.1 Supplier qualification
5.1.1 Requirements for supplier qualification
The requirements for supplier qualification are as follows.

a) The supplier shall have implemented and maintained a documented system for controlling product quality

and design changes. It is assumed that the system includes inspection by the supplier of each lot

produced and the recording of inspection results.

b) The supplier shall have instituted a system that is capable of detecting and correcting shifts in quality

levels and monitoring process changes that may adversely affect quality. The supplier’s personnel

responsible for the application of the system shall demonstrate a clear understanding of the applicable

standards, systems and procedures to be followed.

c) The supplier shall not have experienced any change that might adversely affect quality.

5.1.2 Assessment for supplier qualification

An assessment team may be dispatched for the assessment for supplier qualification. When the assessment

is conducted by the inspection agency, a typical example of what is to be examined and how functions and

responsibilities are shared is shown in Clause 8.

When the purchaser conducts the assessment for supplier qualification, the functions and responsibilities of

the assessment team are similar to those of the inspection agency.

If the supplier has been qualified for another similar product, the responsible authority may consider this fact in

determining the degree of additional assessment for supplier qualification.

The responsible authority shall determine whether the supplier is eligible for skip-lot inspection after reviewing

the assessment results (see 8.2).

Assessment and registration of the supplier in accordance with the third-party assessment standards given in

ISO 9001 for the group of products containing the product concerned should be considered in determining

eligibility for skip-lot inspection.
5.1.3 Verification of supplier qualification

Supplier qualification shall be verified at a frequency agreed to by both the supplier and the responsible

authority. The purpose of this verification is to determine whether or not the supplier is still able to understand

and follow the quality control procedures.

The method of verification is similar to the method of assessment, but it may be simplified so that the review

may be conducted by an inspector in place of an assessment team (see 8.2).
4 © ISO 2005 – All rights reserved
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SIST ISO 2859-3:2006
ISO 2859-3:2005(E)
5.2 Product qualification
5.2.1 Generic requirements for product qualification
Generic requirements for the product qualification are as follows.
a) The product shall be of stable design.

b) The product shall not have any critical classes of nonconforming items or nonconformities.

c) The specified AQL(s) shall be at least 0,025 %. The specified inspection level(s) shall be general

inspection levels I, II or III (see ISO 2859-1).

d) The product shall have been on normal or reduced inspection or a combination of normal and reduced

inspection (see ISO 2859-1) during the qualification period. A product that has been on tightened

inspection at any time during the qualification period is ineligible for skip-lot inspection.

e) The product shall have been produced on an essentially continuous basis for a specified production

period at a specified production frequency.

Both the minimum production period and the minimum production frequency should be specified, based

on the agreement between the supplier and the responsible authority (see Annex A).

If no minimum production period is specified, the period shall be 6 months. Whenever production is held

pending sample approval, only the time period after approval and resumption of production shall be

included.

If no minimum production frequency is specified, the minimum production frequency shall be once per

month, or at least one lot shall be submitted each month.

Products of a similar nature shipped to other parties may be considered in the determination of

“essentially continuous”, if agreed to by both the supplier and the responsible authority.

f) The product quality shall have been maintained at the AQL or better (see ISO 2859-1) for a period of

stability mutually agreed to by both the supplier and the responsible authority. If no period is specified, the

period shall be 6 months.
5.2.2 Specific requirements for product qualification

5.2.2.1 The specific requirements for the product qualification are that the following criteria shall be met:

a) the preceding 10 or more consecutive lots have been accepted on original inspection; the term “on

original inspection” means that the results of resubmitted lots shall not be included;

b) the qualification score (see 5.3) reaches or exceeds 50 within 20 consecutive lots; if the qualification

period exceeds 20 lots, use the qualification score recalculated for the last 20 lots.

5.2.2.2 There are the following limitations on applicable sampling plans:

a) fractional acceptance number sampling plans (see ISO 2859-1:1999, Clause 13) shall not be used;

b) multiple sampling plans are permitted only when the first acceptance number is a numerical value.

5.2.3 Assessment for product qualification

An assessment for product qualification shall not be made prior to the assessment for supplier qualification,

although both assessments may be made at the same time.

The product qualification assessment shall be conducted by an assessment team, an inspector or an

inspection agency. When the assessment is conducted by an inspection agency, a typical example of what is

to be examined and how functions and responsibilities may be shared is shown in Clause 8 and Annex A.

© ISO 2005 – All rights reserved 5
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SIST ISO 2859-3:2006
ISO 2859-3:2005(E)

When the assessment for product qualification is conducted by the purchaser the functions and

responsibilities of the assessment team or the inspector are similar to those of the inspection agency. The

responsible authority shall determine whether the product is eligible for skip-lot inspection after reviewing the

assessment results (see 8.3). Product qualification assessments should always be performed, even in the

case of a supplier with a quality management system certified to be in conformity with ISO 9001.

5.2.4 Verification of product qualification

Product qualification shall be verified at a frequency agreed to by both the supplier and the responsible

authority. The purpose of this verification is to determine whether or not the quality control procedures for the

product continue to be followed. The verification should be made together with the verification for supplier

qualification.

The method of verification is similar to the method of assessment, but it may be simplified (see 8.3).

5.3 Qualification score
5.3.1 General

The qualification score is used not only for qualification, but also for making decisions regarding a change in

frequency, interruption of the procedure, requalification and disqualification. The rules given shall be applied in

the same manner to each state.

In the case of inspection for nonconformities per 100 items, the term “nonconforming item” in the following

rules shall be replaced by “nonconformity”.
5.3.2 Single sampling plans for normal inspection

The rules for calculating the qualification score for normal inspection single sampling plans are as follows:

a) Sampling plans with Ac W 3:

 if the lot would have been accepted had the AQL been two steps tighter, add 5 to the qualification

score;

 if the lot would have been accepted had the AQL been one step but not two steps tighter, add 3 to

the qualification score;
 otherwise reset the qualification score to zero.
b) Sampling plan with Ac = 2:

 if the lot is accepted with no nonconforming item in the sample, add 5 to the qualification score;

 if the lot is accepted with one nonconforming item in the sample, add 3 to the qualification score;

 otherwise reset the qualification score to zero.
c) Sampling plan with Ac = 1:

 if the lot is accepted with no nonconforming item in the sample, add 5 to the qualification score;

 if the lot is accepted with one nonconforming item in the sample, add 1 to the qualification score;

 otherwise reset the qualification score to zero.
d) Sampling plan with Ac = 0:
 if the lot is accepted, add 3 to the qualification score;
 otherwise reset the qualification score to zero.
6 © ISO 2005 – All rights reserved
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SIST ISO 2859-3:2006
ISO 2859-3:2005(E)
5.3.3 Double sampling plans for normal inspection

The rules for calculating the qualification score for normal inspection double sampling plans are as follows:

a) Sampling plans with Ac W 1:

 if the lot would have been accepted after the first sample if the AQL had been one step tighter, add 5

to the qualification score;

 if the lot is accepted after the first sample but would not have been accepted if the AQL had been

one step tighter, add 3 to the qualification score;
 otherwise reset the qualification score to zero.
b) Sampling plan with Ac = 0, Ac = 1 or 3 [Ac = 1 or 2]:
1 2 0

 if the lot is accepted with no nonconforming item in the sample, add 5 to the qualification score;

 if the lot is accepted with one nonconforming item in the cumulative sample, add 1 to the qualification

score;
 otherwise reset the qualification score to zero.
5.3.4 Multiple sampling plans for normal inspection

The rules for calculating the qualification score for normal inspection multiple sampling plans are as follows:

 if the lot is accepted after the first sample, add 5 to the qualification score;

 if the lot is accepted after the second or the third sample, add 3 to the qualification score;

 otherwise reset the qualification score to zero.
Multiple sampling plans are permitted only when Ac W 0.
5.3.5 Sampling plans for reduced inspection

5.3.5.1 For all the single, double and multiple sampling plans for reduced inspection, the rules for the

corresponding normal inspection shall apply, except for the following changes to the values to be added to the

qualification score:
 5 for normal inspection shall be replaced by 3 for reduced inspection;
 3 for normal inspection shall be replaced by 1 for reduced inspection.

5.3.5.2 For example, the rules for reduced inspection single sampling plans with Ac ==== 3 are as follows:

 if the lot would have been accepted had the AQL been two steps tighter, add 3 to the qualification score;

 if the lot would have been accepted had the AQL been one step but not two steps tighter, add 1 to the

qualification score;
 otherwise reset the qualification score to zero.

NOTE Under reduced inspection, 17 or more lots are necessary for qualification. For reduced inspection single

sampling plans with Ac = 0, the qualification score addition is 1 per lot, and will never reach 50 within 20 lots [see 5.2.2 b)].

© ISO 2005 – All
...

SLOVENSKI STANDARD
SIST ISO 2859-3:2006
01-april-2006
3RVWRSNLY]RUþHQMD]DNRQWURORSRRSLVQLKVSUHPHQOMLYNDK±GHO3RVWRSNL
Y]RUþHQMD]L]SXãþDQMHPSDUWLM

Sampling procedures for inspection by attributes -- Part 3: Skip-lot sampling procedures

Règles d'échantillonnage pour les contrôles par attributs -- Partie 3: Procédures

d'échantillonnage successif partiel
Ta slovenski standard je istoveten z: ISO 2859-3:2005
ICS:
03.120.30 8SRUDEDVWDWLVWLþQLKPHWRG Application of statistical
methods
SIST ISO 2859-3:2006 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST ISO 2859-3:2006
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SIST ISO 2859-3:2006
INTERNATIONAL ISO
STANDARD 2859-3
Second edition
2005-05-01
Sampling procedures for inspection by
attributes —
Part 3:
Skip-lot sampling procedures
Règles d'échantillonnage pour les contrôles par attributs —
Partie 3: Procédures d’échantillonnage successif partiel
Reference number
ISO 2859-3:2005(E)
ISO 2005
---------------------- Page: 3 ----------------------
SIST ISO 2859-3:2006
ISO 2859-3:2005(E)
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ii © ISO 2005 – All rights reserved
---------------------- Page: 4 ----------------------
SIST ISO 2859-3:2006
ISO 2859-3:2005(E)
Contents Page

Foreword............................................................................................................................................................ iv

1 Scope...................................................................................................................................................... 1

2 Normative references ........................................................................................................................... 1

3 Terms, definitions and symbols .......................................................................................................... 1

3.1 Terms and definitions........................................................................................................................... 1

3.2 Symbols and abbreviated terms.......................................................................................................... 3

4 General requirements ........................................................................................................................... 3

5 Supplier and product qualification...................................................................................................... 4

5.1 Supplier qualification............................................................................................................................ 4

5.2 Product qualification ............................................................................................................................ 5

5.3 Qualification score................................................................................................................................ 6

5.4 Example for product qualification....................................................................................................... 8

6 Skip-lot sampling procedures ............................................................................................................. 9

6.1 General................................................................................................................................................... 9

6.2 Initial inspection frequency and its determination.......................................................................... 11

6.3 Inspection frequency and shifting .................................................................................................... 11

6.4 Sampling plans, lot selection and inspection procedures (States 2 and 3) ................................. 14

6.5 Skip-lot interruption............................................................................................................................ 15

6.6 Requalification .................................................................................................................................... 16

6.7 Product disqualification ..................................................................................................................... 16

6.8 Supplier disqualification and suspension........................................................................................17

7 Supplier responsibilities .................................................................................................................... 17

8 Inspection agency and responsible authority responsibilities...................................................... 18

8.1 General................................................................................................................................................. 18

8.2 Responsibilities on supplier qualification........................................................................................ 19

8.3 Other responsibilities ......................................................................................................................... 19

9 Compatibility with ISO 2859-1............................................................................................................ 20

9.1 Limitations ........................................................................................................................................... 20

9.2 Relation to reduced inspection ......................................................................................................... 20

10 Additional information........................................................................................................................ 21

10.1 Design basis ........................................................................................................................................ 21

10.2 Statistical characteristics of the skip-lot procedures ..................................................................... 21

Annex A (normative) Optional requirements to be agreed prior to product qualification........................ 23

Annex B (normative) Procedures for random selection at specified inspection frequency .................... 25

Annex C (informative) Factors used in deciding between skip-lot inspection and reduced

inspection ............................................................................................................................................ 27

Bibliography ..................................................................................................................................................... 29

© ISO 2005 – All rights reserved iii
---------------------- Page: 5 ----------------------
SIST ISO 2859-3:2006
ISO 2859-3:2005(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies

(ISO member bodies). The work of preparing International Standards is normally carried out through ISO

technical committees. Each member body interested in a subject for which a technical committee has been

established has the right to be represented on that committee. International organizations, governmental and

non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the

International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International Standards

adopted by the technical committees are circulated to the member bodies for voting. Publication as an

International Standard requires approval by at least 75 % of the member bodies casting a vote.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent

rights. ISO shall not be held responsible for identifying any or all such patent rights.

ISO 2859-3 was prepared by Technical Committee ISO/TC 69, Applications of statistical methods,

Subcommittee SC 5, Acceptance sampling.

This second edition cancels and replaces the first edition (ISO 2859-3:1991), which has been technically

revised.

ISO 2859 consists of the following parts, under the general title Sampling procedures for inspection by

attributes:

 Part 1: Sampling schemes indexed by acceptance quality limit (AQL) for lot-by-lot inspection

 Part 2: Sampling plans indexed by limiting quality (LQ) for isolated lot inspection

 Part 3: Skip-lot sampling procedures
 Part 4: Procedures for assessment of declared quality levels

 Part 5: System of sequential sampling plans indexed by acceptance quality limit (AQL) for lot-by-lot

inspection.
 Part 10: Overview of the ISO 2859 attribute sampling systems
iv © ISO 2005 – All rights reserved
---------------------- Page: 6 ----------------------
SIST ISO 2859-3:2006
INTERNATIONAL STANDARD ISO 2859-3:2005(E)
Sampling procedures for inspection by attributes —
Part 3:
Skip-lot sampling procedures
1 Scope

This part of ISO 2859 specifies generic skip-lot sampling procedures for acceptance inspection by attributes.

The purpose of these procedures is to provide a way of reducing the inspection effort on products of high

quality submitted by a supplier who has a satisfactory quality assurance system and effective quality controls.

The reduction in inspection effort is achieved by determining at random, with a specified probability, whether a

lot presented for inspection will be accepted without inspection. This procedure extends the principle of the

random selection of sample items already applied in ISO 2859-1 to the random selection of lots.

The skip-lot sampling procedures specified in this part of ISO 2859 are applicable to, but not limited to,

inspection of
a) end items, such as complete products or sub-assemblies,
b) components and raw materials, and
c) materials in process.
2 Normative references

The following referenced documents are indispensable for the application of this document. For dated

references, only the edition cited applies. For undated references, the latest edition of the referenced

document (including any amendments) applies.

ISO 2859-1:1999, Sampling procedures for inspection by attributes — Part 1:Sampling schemes indexed by

acceptance quality limit (AQL) for lot-by-lot inspection

ISO 3534-1, Statistics — Vocabulary and symbols — Part 1: Probability and general statistical terms

ISO 3534-2, Statistics — Vocabulary and symbols — Part 2: Applied statistics
3 Terms, definitions and symbols
3.1 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 2859-1, ISO 3534-1, ISO 3534-2

and the following apply. For ease of reference, some terms are quoted from these standards.

3.1.1
continuous production
production that is at a steady rate

NOTE Production is considered continuous if the production has been continued for a specified production period at

a specified production frequency (see 5.2.1). Continuous production is considered a stabilizing factor of the manufacturing

or assembly processes.
© ISO 2005 – All rights reserved 1
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SIST ISO 2859-3:2006
ISO 2859-3:2005(E)
3.1.2
disqualification
failure to qualify for skip-lot sampling inspection (3.1.11)
3.1.3
inspection agency

independent third party with the responsibility for lot inspection and qualification assessment

3.1.4
inspection frequency
probability that a lot is inspected

NOTE Inspection frequencies specified in this part of ISO 2859 are 1/2,1/3,1/4 and 1/5.

3.1.5
interruption

cessation of skip-lot sampling inspection (3.1.11), ending with a return either to skip-lot sampling inspection or

to lot-by-lot inspection
3.1.6
lot-by-lot inspection
inspection of products submitted in a series of lots

NOTE 1 In this part of ISO 2859, a sample (or samples) is (are) drawn from each lot and inspected using acceptance

sampling procedures by attributes given in ISO 2859-1.

NOTE 2 In this part of ISO 2859, lot-by-lot inspection is used both in State 1 (qualification period) and State 3 (skip-lot

interruption state) (see 5.1).
3.1.7
product qualification

assessment of the product to determine its suitability for skip-lot sampling inspection (3.1.11)

3.1.8
qualification score

running total derived according to given rules from the immediately preceding quality history, and used in

making decisions regarding qualification, changes in inspection frequency (3.1.4), interruption (3.1.5),

disqualification (3.1.2) and requalification (3.1.9)
3.1.9
requalification
qualification for a resumption of skip-lot sampling inspection (3.1.11)
3.1.10
responsible authority

person or group of people who has responsibility and authority to manage inspection systems appropriately

NOTE In this part of ISO 2859, the responsible authority has responsibility and authority to assess and verify supplier

qualification, decide various criteria and judge switch inspection stages.
3.1.11
skip-lot sampling inspection

sampling inspection procedure in which some lots in a series are accepted without inspection when the

sampling results for a stated number of immediately preceding lots meet stated criteria

NOTE The lots to be inspected are chosen randomly in accordance with a stated (skip-lot) inspection frequency. An

inspection frequency of 1 in 2, for example, means that the long run average proportion of lots inspected is 1/2.

2 © ISO 2005 – All rights reserved
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SIST ISO 2859-3:2006
ISO 2859-3:2005(E)
3.1.12
supplier qualification

assessment of the supplier’s competence to implement skip-lot sampling inspection (3.1.11)

3.2 Symbols and abbreviated terms
The symbols and abbreviated terms used in this document are as follows:
Ac acceptance number;
Ac acceptance number for the corresponding single sampling plan;
Ac first acceptance number (for the double or multiple sampling plan);
Ac second acceptance number (for the double or multiple sampling plan);
d number of nonconforming items or nonconformities in the sample;

k number of lots used for inspection frequency (the inspection frequency is 1 in k; i.e. 1/k);

n sample size.
4 General requirements

4.1 Skip-lot inspection may only be used when both the supplier and the product are qualified. The

requirements for qualification are specified in Clause 5.

NOTE The skip-lot sampling procedures specified in this part of ISO 2859 should be distinguished from Dodge’s

skip-lot sampling plans. See [1], [2] and [3] in the Bibliography.

4.2 This part of ISO 2859 is intended to supplement the ISO 2859-1 sampling system, and may be used

together with ISO 2859-1. Unless otherwise specified in this part of ISO 2859, the provisions of ISO 2859-1

shall apply. ISO 2859-10 provides useful information concerning the use of the standards in the ISO 2859

series.

4.3 The skip-lot sampling procedures specified in this part of ISO 2859 are intended only for a continuing

series of lots and shall not be used for isolated lots. All lots in the series are expected to be of a similar quality

and there should be reason to believe that lots not inspected are of the same quality as the ones inspected.

4.4 Skip-lot sampling may be used instead of reduced inspection if it is more cost effective to do so (see 9.2

and Annex C), but its application and switching rules are different from those of reduced inspection in

ISO 2859-1.

4.5 There are some limitations to the use of skip-lot sampling procedures (see 9.1).

4.6 When different acceptance quality limit (AQL) values are specified for two or more classes of

nonconforming items or nonconformities, special care should be taken to ensure correct application of the

standard (see 5.2.2 to 6.6 and 10.2).

4.7 Inspection may take place at the supplier’s or purchaser’s locations, or at an interface between

operations of a production process.

4.8 As every product has its own environment and characteristics, options are provided so that the supplier

and the responsible authority may select the appropriate options to meet the specifics of the product and its

environment. All choices as a result of this tailoring should be specified in a written document.

4.9 When specified by the purchaser, this part of ISO 2859 may be referenced in a purchasing or

specification contract, inspection instruction, or other contractual documents.
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SIST ISO 2859-3:2006
ISO 2859-3:2005(E)

4.10 The responsible authority and the inspection agency are to be designated in one of the above

documents. This part of ISO 2859 assumes that both lot inspection and qualification assessment are

conducted by an inspection agency, being an independent third party. However, the purchaser may conduct

both. It is necessary to replace the term “inspection agency” by “purchaser’s inspector” or “assessing team” as

occasion demands (see 5.1.2, 5.2.3 and Clauses 7 and 8).
5 Supplier and product qualification
5.1 Supplier qualification
5.1.1 Requirements for supplier qualification
The requirements for supplier qualification are as follows.

a) The supplier shall have implemented and maintained a documented system for controlling product quality

and design changes. It is assumed that the system includes inspection by the supplier of each lot

produced and the recording of inspection results.

b) The supplier shall have instituted a system that is capable of detecting and correcting shifts in quality

levels and monitoring process changes that may adversely affect quality. The supplier’s personnel

responsible for the application of the system shall demonstrate a clear understanding of the applicable

standards, systems and procedures to be followed.

c) The supplier shall not have experienced any change that might adversely affect quality.

5.1.2 Assessment for supplier qualification

An assessment team may be dispatched for the assessment for supplier qualification. When the assessment

is conducted by the inspection agency, a typical example of what is to be examined and how functions and

responsibilities are shared is shown in Clause 8.

When the purchaser conducts the assessment for supplier qualification, the functions and responsibilities of

the assessment team are similar to those of the inspection agency.

If the supplier has been qualified for another similar product, the responsible authority may consider this fact in

determining the degree of additional assessment for supplier qualification.

The responsible authority shall determine whether the supplier is eligible for skip-lot inspection after reviewing

the assessment results (see 8.2).

Assessment and registration of the supplier in accordance with the third-party assessment standards given in

ISO 9001 for the group of products containing the product concerned should be considered in determining

eligibility for skip-lot inspection.
5.1.3 Verification of supplier qualification

Supplier qualification shall be verified at a frequency agreed to by both the supplier and the responsible

authority. The purpose of this verification is to determine whether or not the supplier is still able to understand

and follow the quality control procedures.

The method of verification is similar to the method of assessment, but it may be simplified so that the review

may be conducted by an inspector in place of an assessment team (see 8.2).
4 © ISO 2005 – All rights reserved
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SIST ISO 2859-3:2006
ISO 2859-3:2005(E)
5.2 Product qualification
5.2.1 Generic requirements for product qualification
Generic requirements for the product qualification are as follows.
a) The product shall be of stable design.

b) The product shall not have any critical classes of nonconforming items or nonconformities.

c) The specified AQL(s) shall be at least 0,025 %. The specified inspection level(s) shall be general

inspection levels I, II or III (see ISO 2859-1).

d) The product shall have been on normal or reduced inspection or a combination of normal and reduced

inspection (see ISO 2859-1) during the qualification period. A product that has been on tightened

inspection at any time during the qualification period is ineligible for skip-lot inspection.

e) The product shall have been produced on an essentially continuous basis for a specified production

period at a specified production frequency.

Both the minimum production period and the minimum production frequency should be specified, based

on the agreement between the supplier and the responsible authority (see Annex A).

If no minimum production period is specified, the period shall be 6 months. Whenever production is held

pending sample approval, only the time period after approval and resumption of production shall be

included.

If no minimum production frequency is specified, the minimum production frequency shall be once per

month, or at least one lot shall be submitted each month.

Products of a similar nature shipped to other parties may be considered in the determination of

“essentially continuous”, if agreed to by both the supplier and the responsible authority.

f) The product quality shall have been maintained at the AQL or better (see ISO 2859-1) for a period of

stability mutually agreed to by both the supplier and the responsible authority. If no period is specified, the

period shall be 6 months.
5.2.2 Specific requirements for product qualification

5.2.2.1 The specific requirements for the product qualification are that the following criteria shall be met:

a) the preceding 10 or more consecutive lots have been accepted on original inspection; the term “on

original inspection” means that the results of resubmitted lots shall not be included;

b) the qualification score (see 5.3) reaches or exceeds 50 within 20 consecutive lots; if the qualification

period exceeds 20 lots, use the qualification score recalculated for the last 20 lots.

5.2.2.2 There are the following limitations on applicable sampling plans:

a) fractional acceptance number sampling plans (see ISO 2859-1:1999, Clause 13) shall not be used;

b) multiple sampling plans are permitted only when the first acceptance number is a numerical value.

5.2.3 Assessment for product qualification

An assessment for product qualification shall not be made prior to the assessment for supplier qualification,

although both assessments may be made at the same time.

The product qualification assessment shall be conducted by an assessment team, an inspector or an

inspection agency. When the assessment is conducted by an inspection agency, a typical example of what is

to be examined and how functions and responsibilities may be shared is shown in Clause 8 and Annex A.

© ISO 2005 – All rights reserved 5
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SIST ISO 2859-3:2006
ISO 2859-3:2005(E)

When the assessment for product qualification is conducted by the purchaser the functions and

responsibilities of the assessment team or the inspector are similar to those of the inspection agency. The

responsible authority shall determine whether the product is eligible for skip-lot inspection after reviewing the

assessment results (see 8.3). Product qualification assessments should always be performed, even in the

case of a supplier with a quality management system certified to be in conformity with ISO 9001.

5.2.4 Verification of product qualification

Product qualification shall be verified at a frequency agreed to by both the supplier and the responsible

authority. The purpose of this verification is to determine whether or not the quality control procedures for the

product continue to be followed. The verification should be made together with the verification for supplier

qualification.

The method of verification is similar to the method of assessment, but it may be simplified (see 8.3).

5.3 Qualification score
5.3.1 General

The qualification score is used not only for qualification, but also for making decisions regarding a change in

frequency, interruption of the procedure, requalification and disqualification. The rules given shall be applied in

the same manner to each state.

In the case of inspection for nonconformities per 100 items, the term “nonconforming item” in the following

rules shall be replaced by “nonconformity”.
5.3.2 Single sampling plans for normal inspection

The rules for calculating the qualification score for normal inspection single sampling plans are as follows:

a) Sampling plans with Ac W 3:

 if the lot would have been accepted had the AQL been two steps tighter, add 5 to the qualification

score;

 if the lot would have been accepted had the AQL been one step but not two steps tighter, add 3 to

the qualification score;
 otherwise reset the qualification score to zero.
b) Sampling plan with Ac = 2:

 if the lot is accepted with no nonconforming item in the sample, add 5 to the qualification score;

 if the lot is accepted with one nonconforming item in the sample, add 3 to the qualification score;

 otherwise reset the qualification score to zero.
c) Sampling plan with Ac = 1:

 if the lot is accepted with no nonconforming item in the sample, add 5 to the qualification score;

 if the lot is accepted with one nonconforming item in the sample, add 1 to the qualification score;

 otherwise reset the qualification score to zero.
d) Sampling plan with Ac = 0:
 if the lot is accepted, add 3 to the qualification score;
 otherwise reset the qualification score to zero.
6 © ISO 2005 – All rights reserved
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SIST ISO 2859-3:2006
ISO 2859-3:2005(E)
5.3.3 Double sampling plans for normal inspection

The rules for calculating the qualification score for normal inspection double sampling plans are as follows:

a) Sampling plans with Ac W 1:

 if the lot would have been accepted after the first sample if the AQL had been one step tighter, add 5

to the qualification score;

 if the lot is accepted after the first sample but would not have been accepted if the AQL had been

one step tighter, add 3 to the qualification score;
 otherwise reset the qualification score to zero.
b) Sampling plan with Ac = 0, Ac = 1 or 3 [Ac = 1 or 2]:
1 2 0

 if the lot is accepted with no nonconforming item in the sample, add 5 to the qualification score;

 if the lot is accepted with one nonconforming item in the cumulative sample, add 1 to the qualification

score;
 otherwise reset the qualification score to zero.
5.3.4 Multiple sampling plans for normal inspection

The rules for calculating the qualification score for normal inspection multiple sampling plans are as follows:

 if the lot is accepted after the first sample, add 5 to the qualification score;

 if the lot is accepted after the second or the third sample, add 3 to the qualification score;

 otherwise reset the qualification score to zero.
Multiple sampling plans are permitted only when Ac W 0.
5.3.5 Sampling plans for reduced inspection

5.3.5.1 For all the single, double and multiple sampling plans for reduced inspection, the rules for the

corresponding normal inspection shall apply, except for the following changes to the values to be added to the

qualification score:
 5 for normal inspection shall be replaced by 3 for reduced inspection;
 3 for normal inspection shall be replaced by 1 for reduced inspection.

5.3.5.2 For example, the rules for reduced inspection single sampling plans with Ac ==== 3 are as follows:

 if the lot would have been accepted had the AQL been two steps tighter, add 3 to the qualification score;

 if the lot would have been accepted had the AQL been one step but not two steps tighter, add 1 to the

qualification score;
 otherwise reset the qualification score to zero.

NOTE Under reduced inspection, 17 or more lots are necessary for qualification. For reduced inspection single

sampling plans with Ac = 0, the qualification score addition is 1 per lot, and will never reach 50 within 20 lots [see 5.2.2

...

NORME ISO
INTERNATIONALE 2859-3
Deuxième édition
2005-05-01
Règles d'échantillonnage pour les
contrôles par attributs —
Partie 3:
Procédures d'échantillonnage successif
partiel
Sampling procedures for inspection by attributes —
Part 3: Skip-lot sampling procedures
Numéro de référence
ISO 2859-3:2005(F)
ISO 2005
---------------------- Page: 1 ----------------------
ISO 2859-3:2005(F)
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ii © ISO 2005 – Tous droits réservés
---------------------- Page: 2 ----------------------
ISO 2859-3:2005(F)
Sommaire Page

Avant-propos..................................................................................................................................................... iv

1 Domaine d'application.......................................................................................................................... 1

2 Références normatives......................................................................................................................... 1

3 Termes, définitions et symboles ......................................................................................................... 1

3.1 Termes et définitions ............................................................................................................................ 1

3.2 Symboles et termes abrégés ............................................................................................................... 3

4 Exigences générales............................................................................................................................. 3

5 Qualification du fournisseur et du produit......................................................................................... 4

5.1 Qualification du fournisseur ................................................................................................................ 4

5.2 Qualification du produit........................................................................................................................ 5

5.3 Score de qualification........................................................................................................................... 6

5.4 Exemple de qualification d'un produit................................................................................................ 8

6 Procédures d'échantillonnage successif partiel ............................................................................... 9

6.1 Généralités............................................................................................................................................. 9

6.2 Fréquence de contrôle initiale et sa détermination......................................................................... 10

6.3 Fréquence de contrôle et changement de fréquence ..................................................................... 12

6.4 Plans d'échantillonnage, sélection de lots et procédures de contrôle (États 2 et 3)................... 15

6.5 Interruption du contrôle par échantillonnage successif partiel..................................................... 15

6.6 Requalification .................................................................................................................................... 16

6.7 Disqualification du produit................................................................................................................. 17

6.8 Disqualification du fournisseur et suspension................................................................................ 18

7 Responsabilités du fournisseur ........................................................................................................ 18

8 Responsabilités de l'organisme de contrôle et de l'autorité responsable.................................... 19

8.1 Généralités........................................................................................................................................... 19

8.2 Responsabilités de la qualification du fournisseur......................................................................... 19

8.3 Autres responsabilités ....................................................................................................................... 20

9 Compatibilité avec l'ISO 2859-1 ......................................................................................................... 21

9.1 Limites.................................................................................................................................................. 21

9.2 Lien avec le contrôle réduit................................................................................................................ 21

10 Renseignements complémentaires................................................................................................... 21

10.1 Base de la conception ........................................................................................................................ 21

10.2 Caractéristiques statistiques des procédures d'échantillonnage successif partiel.................... 22

Annexe A (normative) Résumé des options à confirmer avant la qualification du produit ..................... 24

Annexe B (normative) Procédures de sélection aléatoire à une fréquence de contrôle spécifiée.......... 26

Annexe C (informative) Facteurs utilisés pour se décider entre un contrôle par échantillonnage

successif partiel et un contrôle réduit .............................................................................................. 28

Bibliographie .................................................................................................................................................... 30

© ISO 2005 – Tous droits réservés iii
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ISO 2859-3:2005(F)
Avant-propos

L'ISO (Organisation internationale de normalisation) est une fédération mondiale d'organismes nationaux de

normalisation (comités membres de l'ISO). L'élaboration des Normes internationales est en général confiée

aux comités techniques de l'ISO. Chaque comité membre intéressé par une étude a le droit de faire partie du

comité technique créé à cet effet. Les organisations internationales, gouvernementales et non

gouvernementales, en liaison avec l'ISO participent également aux travaux. L'ISO collabore étroitement avec

la Commission électrotechnique internationale (CEI) en ce qui concerne la normalisation électrotechnique.

Les Normes internationales sont rédigées conformément aux règles données dans les Directives ISO/CEI,

Partie 2.

La tâche principale des comités techniques est d'élaborer les Normes internationales. Les projets de Normes

internationales adoptés par les comités techniques sont soumis aux comités membres pour vote. Leur

publication comme Normes internationales requiert l'approbation de 75 % au moins des comités membres

votants.

L'attention est appelée sur le fait que certains des éléments du présent document peuvent faire l'objet de

droits de propriété intellectuelle ou de droits analogues. L'ISO ne saurait être tenue pour responsable de ne

pas avoir identifié de tels droits de propriété et averti de leur existence.

L'ISO 2859-3 a été élaborée par le comité technique ISO/TC 69, Application des méthodes statistiques,

sous-comité SC 5, Échantillonnage en vue d'acceptation.

Cette deuxième édition annule et remplace la première édition (ISO 2859-3:1991), dont elle constitue une

révision technique.

L'ISO 2859 comprend les parties suivantes, présentées sous le titre général Règles d'échantillonnage pour

les contrôles par attributs:

 Partie 1: Procédures d'échantillonnage pour les contrôles lot par lot, indexés d'après le niveau de qualité

acceptable (NQA)

 Partie 2: Plans d'échantillonnage pour les contrôles de lots isolés, indexés d'après la qualité limite (QL)

 Partie 3: Procédures d'échantillonnage successif partiel
 Partie 4: Procédures pour l'évaluation des niveaux déclarés de qualité

 Partie 5: Systèmes de plans d'échantillonnage progressif pour le contrôle lot par lot, indexés d'après le

niveau de qualité acceptable (NQA)

 Partie 10: Vue d'ensemble du système d'échantillonnage par attributs de l'ISO 2859

iv © ISO 2005 – Tous droits réservés
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NORME INTERNATIONALE ISO 2859-3:2005(F)
Règles d'échantillonnage pour les contrôles par attributs —
Partie 3:
Procédures d'échantillonnage successif partiel
1 Domaine d'application

La présente partie de l'ISO 2859 spécifie des procédures génériques d'échantillonnage successif partiel

destinées à un contrôle par attributs pour acceptation. L'objectif de ces procédures est de fournir un moyen de

réduire les efforts de contrôle sur des produits de haute qualité présentés par un fournisseur disposant d'un

système d'assurance de la qualité satisfaisant et de contrôles de la qualité efficaces. La réduction des efforts

de contrôle est obtenue en déterminant de manière aléatoire, avec une probabilité spécifiée, si un lot présenté

au contrôle sera accepté sans contrôle. Cette procédure élargit le principe de sélection aléatoire d'individus

d'échantillonnage, déjà appliqué dans l'ISO 2859-1, à la sélection aléatoire de lots.

Les procédures d'échantillonnage successif partiel contenues dans la présente partie de l'ISO 2859 sont

applicables, mais d'une manière non limitative, aux contrôles:
a) de produits finis tels que des produits ou sous-ensembles complets;
b) de composants et de matières premières, et
c) de matériaux en cours de fabrication.
2 Références normatives

Les documents de référence suivants sont indispensables pour l'application du présent document. Pour les

références datées, seule l'édition citée s'applique. Pour les références non datées, la dernière édition du

document de référence s'applique (y compris les éventuels amendements).

ISO 2859-1:1999, Règles d'échantillonnage pour les contrôles par attributs — Partie 1: Procédures

d'échantillonnage pour les contrôles lot par lot, indexés d'après le niveau de qualité acceptable (NQA)

ISO 3534-1, Statistique — Vocabulaire et symboles — Partie 1: Probabilité et termes statistiques généraux

ISO 3534-2, Statistique — Vocabulaire et symboles — Partie 2: Statistique appliquée

3 Termes, définitions et symboles
3.1 Termes et définitions

Pour les besoins du présent document, les termes et définitions donnés dans l'ISO 2859-1, dans l'ISO 3534-1

et dans l'ISO 3534-2 s'appliquent. Pour faciliter la référence, certains termes sont repris de ces normes.

3.1.1
production continue
production à un rythme constant

NOTE La production est considérée comme continue si elle se poursuit pendant une période de production définie à

une fréquence de production définie (voir 5.2.1). La production continue est considérée comme un facteur stabilisant des

processus de fabrication ou d'assemblage.
© ISO 2005 – Tous droits réservés 1
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ISO 2859-3:2005(F)
3.1.2
disqualification

absence de qualification pour un contrôle par échantillonnage successif partiel (3.1.11)

3.1.3
organisme de contrôle

tierce partie indépendante responsable du contrôle par lot et de l'évaluation de la qualité

3.1.4
fréquence de contrôle
probabilité qu'un lot soit contrôlé

NOTE Les fréquences de contrôle spécifiées dans la présente partie de l'ISO 2859 sont 1/2, 1/3, 1/4 et 1/5.

3.1.5
interruption

cessation du contrôle par échantillonnage successif partiel (3.1.11) se terminant par un retour au contrôle par

échantillonnage successif partiel ou au contrôle lot par lot
3.1.6
contrôle lot par lot
contrôle d'un produit présenté dans une série de lots

NOTE 1 Dans la présente partie de l'ISO 2859, un (des) échantillon(s) est (sont) tiré(s) de chaque lot et contrôlé(s)

selon les procédures d'échantillonnage pour acceptation par attributs indiquées dans l'ISO 2859-1.

NOTE 2 Dans la présente partie de l'ISO 2859, le contrôle lot par lot est utilisé à la fois dans l'État 1 (période de

qualification) et dans l'État 3 (état d'interruption du contrôle par échantillonnage successif partiel) (voir 5.1).

3.1.7
qualification du produit

évaluation du produit pour déterminer s'il convient à un contrôle par échantillonnage successif partiel (3.1.11)

3.1.8
score de qualification

total en cours selon des règles données, issues de l'historique qualité immédiatement précédent, et utilisé

pour prendre des décisions concernant la qualification, les changements de fréquence de contrôle (3.1.4),

l'interruption (3.1.5), la disqualification (3.1.2) et la requalification (3.1.9)

3.1.9
requalification

qualification pour une reprise du contrôle par échantillonnage successif partiel (3.1.11)

3.1.10
autorité responsable

personne ou groupe de personnes ayant la responsabilité et le pouvoir de diriger les systèmes de contrôle

comme il se doit

NOTE Dans la présente partie de l'ISO 2859, l'autorité responsable a la responsabilité et le pouvoir d'évaluer et de

vérifier la qualification des fournisseurs, de décider divers critères et de juger les étapes de contrôle de transition.

3.1.11
contrôle par échantillonnage successif partiel

procédure de contrôle par échantillonnage où certains lots d'une série sont acceptés sans contrôle quand les

résultats de l'échantillonnage d'un nombre fixé de lots les précédant immédiatement répondent aux critères

spécifiés

NOTE Les lots à contrôler sont choisis de manière aléatoire, selon la fréquence de contrôle (par échantillonnage

successif partiel) indiquée. Par exemple, une fréquence de contrôle de 1 sur 2 signifie que la proportion moyenne à long

terme de lots contrôlés est égale à 1/2.
2 © ISO 2005 – Tous droits réservés
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ISO 2859-3:2005(F)
3.1.12
qualification du fournisseur

évaluation des compétences du fournisseur à mettre en place un contrôle par échantillonnage successif

partiel (3.1.11)
3.2 Symboles et termes abrégés
Les symboles utilisés dans le présent document sont les suivants:
Ac critère d'acceptation;
Ac critère d'acceptation pour le plan d'échantillonnage simple correspondant;

Ac premier critère d'acceptation (pour le plan d'échantillonnage double ou multiple);

Ac second critère d'acceptation (pour le plan d'échantillonnage double ou multiple);

d nombre d'individus non conformes ou de non-conformités dans l'échantillon;

k nombre de lots utilisés pour la fréquence de contrôle (la fréquence de contrôle est de 1 sur k ou 1/k);

n effectif d'échantillon.
4 Exigences générales

4.1 Le contrôle par échantillonnage successif partiel ne peut être utilisé que lorsque le fournisseur et le

produit sont qualifiés tous les deux. Les exigences relatives à la qualification sont spécifiées à l'Article 5.

NOTE Il convient de distinguer les procédures d'échantillonnage successif partiel, spécifiées dans la présente partie

de l'ISO 2859, des plans d'échantillonnage successif partiel de Dodge. Voir [1], [2] et [3] dans la Bibliographie.

4.2 La présente partie de l'ISO 2859 est destinée à compléter le système d'échantillonnage de l'ISO 2859-1

et peut être utilisée conjointement avec l'ISO 2859-1. Sauf spécification contraire dans la présente partie de

l'ISO 2859, les dispositions de l'ISO 2859-1 doivent s'appliquer. L'ISO 2859-10 fournit des informations utiles

sur l'utilisation des normes de la série ISO 2859.

4.3 Les procédures d'échantillonnage successif partiel spécifiées dans la présente partie de l'ISO 2859 sont

destinées seulement à une série continue de lots et ne doivent pas être utilisées pour des lots isolés. On

s'attend à ce que tous les lots de la série soient d'une qualité similaire et il convient d'avoir des raisons de

penser que les lots non contrôlés sont de la même qualité que les lots contrôlés.

4.4 Le contrôle par échantillonnage successif partiel peut être utilisé à la place du contrôle réduit s'il est

plus rentable de procéder ainsi (voir 9.2 et l'Annexe C), mais l'application et les règles de modification du

contrôle sont différentes de celles du contrôle réduit spécifié dans l'ISO 2859-1.

4.5 Il existe certaines limites à l'utilisation de procédures d'échantillonnage successif partiel (voir 9.1).

4.6 Lorsque différentes valeurs du niveau de qualité acceptable (NQA) sont spécifiées pour deux

catégories ou plus d'individus non conformes ou de non-conformités, il convient d'y accorder une attention

particulière pour assurer la bonne application de la norme (voir 5.2.2 à 6.6 et 10.2).

4.7 Le contrôle peut avoir lieu dans les locaux du fournisseur ou de l'acheteur ou dans un endroit faisant

l'interface entre les opérations d'un processus de production.

4.8 Chaque produit ayant son propre environnement et ses propres caractéristiques, des options sont

fournies de manière que le fournisseur et l'autorité responsable puissent sélectionner les options appropriées

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pour répondre aux spécificités du produit et de son environnement. Il convient de spécifier dans un document

écrit tous les choix issus de ces spécificités.

4.9 Si l'acheteur le spécifie, la présente partie de l'ISO 2859 peut être indiquée comme référence dans un

contrat d'achat ou de spécification, dans des instructions de contrôle ou autres documents contractuels.

4.10 L'autorité responsable et l'organisme de contrôle seront désignés dans l'un des documents indiqués

ci-dessus. La présente partie de l'ISO 2859 suppose qu'à la fois le contrôle par lot et l'évaluation de

qualification sont réalisés par un organisme de contrôle qui est une tierce partie indépendante. Les deux

peuvent cependant être réalisés par l'acheteur. Il est alors nécessaire de remplacer le terme «organisme de

contrôle» par le terme «contrôleur de l'acheteur» ou «équipe d'évaluation» selon le cas (voir 5.1.2, 5.2.3 et les

Articles 7 et 8).
5 Qualification du fournisseur et du produit
5.1 Qualification du fournisseur
5.1.1 Exigences relatives à la qualification du fournisseur
Les exigences relatives à la qualification du fournisseur sont les suivantes.

a) Le fournisseur doit avoir mis en œuvre et maintenu un système documenté pour contrôler la qualité des

produits et les modifications de conception. On suppose que ce système comprend le contrôle par le

fournisseur de chaque lot produit et l'enregistrement des résultats du contrôle.

b) Le fournisseur doit avoir institué un système capable de détecter et de corriger les changements de

niveaux de qualité et les modifications du processus de surveillance qui peuvent avoir des effets négatifs

sur la qualité. Le personnel responsable de l'application du système chez le fournisseur doit avoir une

bonne compréhension des normes applicables, des systèmes et procédures à suivre.

c) Le fournisseur ne doit pas avoir connu de modifications susceptibles d'avoir des effets négatifs sur la

qualité.
5.1.2 Évaluation pour la qualification du fournisseur

L'évaluation pour la qualification du fournisseur peut être confiée à une équipe d'évaluation. Lorsque

l'évaluation est réalisée par un organisme de contrôle, se reporter à l'Article 8 présentant un exemple type ce

qui est à examiner et de la façon dont les fonctions et les responsabilités sont partagées.

Lorsque l'acheteur réalise l'évaluation pour la qualification du fournisseur, les fonctions et les responsabilités

de l'équipe d'évaluation sont similaires à celles d'un organisme de contrôle.

Si le fournisseur a été qualifié pour un autre produit similaire, l'autorité responsable peut en tenir compte dans

la détermination du degré d'évaluation supplémentaire pour la qualification du fournisseur.

Après avoir examiné les résultats de l'évaluation (voir 8.2), l'autorité responsable doit déterminer si le

fournisseur est apte à subir un contrôle par échantillonnage successif partiel.

Si le fournisseur a été évalué et enregistré conformément aux normes d'évaluation par tierce partie figurant

dans l'ISO 9001, pour le groupe de produits incluant le produit concerné, il convient de considérer le

fournisseur comme apte à subir un contrôle par échantillonnage successif partiel.

5.1.3 Vérification de la qualification du fournisseur

La qualification du fournisseur doit être vérifiée à une fréquence convenue entre le fournisseur et l'autorité

responsable. Cette vérification a pour objectif de déterminer si le fournisseur est toujours capable ou non de

comprendre et de suivre les procédures de contrôle de la qualité.
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Cette méthode de vérification est identique à la méthode d'évaluation, mais elle peut être simplifiée dans la

mesure où l'examen peut être conduit par un contrôleur au lieu de l'équipe d'évaluation (voir 8.2).

5.2 Qualification du produit
5.2.1 Exigences générales relatives à la qualification du produit

Les exigences générales relatives à la qualification du produit sont les suivantes:

a) Le produit doit avoir une conception établie.

b) Le produit ne doit pas comporter de catégories critiques d'individus non conformes ou de non-conformités.

c) Le(s) NQA spécifié(s) doit (doivent) être d'au moins 0,025 %. Le(s) niveau(x) de contrôle spécifié(s) doit

(doivent) être les niveaux I, II ou III pour usages généraux (voir l'ISO 2859-1).

d) Le produit doit avoir été soumis à un contrôle normal ou à un contrôle réduit ou à une combinaison des

deux (voir l'ISO 2859-1) pendant la période de qualification. Un produit qui a subi un contrôle renforcé à

n'importe quel moment de la période de qualification n'est pas apte à un contrôle par échantillonnage

successif partiel.

e) Le produit doit avoir été fabriqué de manière essentiellement continue pendant une période de production

définie à une fréquence de production définie.

Il convient de spécifier à la fois la période de production minimale et la fréquence de production minimale,

sur la base de l'accord conclu entre le fournisseur et l'autorité responsable (voir l'Annexe A).

Si aucune période de production minimale n'est spécifiée, la période doit être de six mois. Si la

production est suspendue en attendant l'approbation d'échantillons, seule la période postérieure à

l'approbation et à la reprise de la production doit être prise en compte.

Si aucune fréquence de production minimale n'est spécifiée, la fréquence de production minimale doit

être d'une fois par mois, ou bien au moins un lot doit être présenté chaque mois.

Les produits de même nature expédiés à d'autres parties peuvent être pris en compte dans la

détermination du terme «essentiellement continu», si cela est convenu entre le fournisseur et l'autorité

responsable.

f) La qualité du produit doit être maintenue au NQA ou à un meilleur niveau (voir l'ISO 2859-1) pendant une

période de stabilité convenue mutuellement entre le fournisseur et l'autorité responsable. Si aucune

période n'est spécifiée, la période doit être de six mois.
5.2.2 Exigences spécifiques relatives à la qualification du produit

5.2.2.1 Selon les exigences spécifiques relatives à la qualification du produit, les critères suivants doivent

être remplis:

a) les 10 lots ou plus consécutifs précédents ont été acceptés suite à un contrôle en première présentation.

Le terme «en première présentation» signifie que les résultats de lots présentés à nouveau ne doivent

pas être inclus;

b) le score de qualification (voir 5.3) est supérieur ou égal à 50 pour 20 lots, si la période de qualification

dépasse 20 lots, utiliser le score de qualification recalculé pour les 20 derniers lots.

5.2.2.2 Les plans d'échantillonnage applicables sont soumis aux limites suivantes:

a) les plans d'échantillonnage à critère d'acceptation décimal (voir l'ISO 2859-1:1999, Article 13) ne doivent

pas être utilisés;

b) les plans d'échantillonnage multiple sont permis uniquement si le premier critère d'acceptation est une

valeur numérique.
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5.2.3 Évaluation pour la qualification du produit

L'évaluation pour la qualification du produit ne doit pas être réalisée avant l'évaluation pour la qualification du

fournisseur. Cependant, les deux évaluations peuvent être effectuées en même temps.

L'évaluation pour la qualification du produit est conduite par une équipe d'évaluation, par un contrôleur ou par

un organisme de contrôle. Lorsque l'évaluation est réalisée par un organisme de contrôle, se reporter à

l'Article 8 et à l'Annexe A présentant un exemple type de ce qui est à examiner et de la façon dont les

fonctions et les responsabilités peuvent être partagées.

Lorsque l'acheteur réalise l'évaluation pour la qualification du produit, les fonctions et les responsabilités de

l'équipe d'évaluation ou du contrôleur sont les mêmes que celles de l'organisme de contrôle. Après avoir

examiné les résultats de l'évaluation (voir 8.3), l'autorité responsable doit déterminer si le produit est apte à un

contrôle par échantillonnage successif partiel. Il convient de toujours réaliser les évaluations pour la

qualification du produit même pour un fournisseur dont le système de management de la qualité a été déclaré

conforme à l'ISO 9001.
5.2.4 Vérification de la qualification du produit

La qualification du produit doit être vérifiée à une fréquence convenue entre le fournisseur et l'autorité

responsable. Cette vérification a pour objectif de déterminer si les procédures de contrôle de la qualité du

produit continuent d'être suivies. Il convient de procéder à cette vérification en même temps qu'à la vérification

pour la qualification du fournisseur.

Cette méthode de vérification est identique à la méthode d'évaluation, mais elle peut être simplifiée (voir 8.3).

5.3 Score de qualification
5.3.1 Généralités

Le score de qualification n'est pas seulement utilisé pour la qualification, mais également pour prendre des

décisions concernant une modification de fréquence, l'interruption de la procédure, la requalification et la

disqualification. Les règles énoncées doivent s'appliquer de la même manière à chaque état.

En cas de contrôle de non-conformités pour 100 individus, le terme «individu non conforme» doit être

remplacé par «non-conformité» dans les règles suivantes.
5.3.2 Plans d'échantillonnage simple pour un contrôle normal

Les règles de calcul du score de qualification pour des plans d'échantillonnage simple dans le cadre d'un

contrôle normal sont les suivantes:
a) plans d'échantillonnage où Ac W 3:

 si le lot aurait été accepté avec un NQA plus sévère de deux niveaux, ajouter 5 au score de

qualification;

 si le lot aurait été accepté avec un NQA plus sévère d'un niveau mais non de deux niveaux, ajouter 3

au score de qualification;
 sinon, remettre le score de qualification à zéro;
b) plans d'échantillonnage où Ac = 2:

 si le lot est accepté sans aucun individu non conforme dans l'échantillon, ajouter 5 au score de

qualification;
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 si le lot est accepté avec un individu non conforme dans l'échantillon, ajouter 3 au score de

qualification;
 sinon, remettre le score de qualification à zéro;
c) plans d'échantillonnage où Ac = 1:

 si le lot est accepté sans aucun individu non conforme dans l'échantillon, ajouter 5 au score de

qualification;

 si le lot est accepté avec un individu non conforme dans l'échantillon, ajouter 1 au score de

qualification;
 sinon, remettre le score de qualification à zéro;
d) plans d'échantillonnage où Ac = 0:
 si le lot est accepté, ajouter 3 au score de qualification;
 sinon, remettre le score de qualification à zéro.
5.3.3 Plans d'échantillonnage double pour un contrôle normal

Les règles de calcul du score de qualification pour des plans d'échantillonnage double dans le cadre d'un

contrôle normal sont les suivantes:
a) plans d'échantillonnage où Ac W 1:
 si le lot aurait été a
...

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