ASTM E1994-08
(Practice)Standard Practice for Use of Process Oriented AOQL and LTPD Sampling Plans
Standard Practice for Use of Process Oriented AOQL and LTPD Sampling Plans
SIGNIFICANCE AND USE
Two general types of tables (Note 1) are given, one based on the concept of lot tolerance, LTPD, and the other on AOQL. The broad conditions under which the different types have been found best adapted are indicated below.
For each of the types, tables are provided both for single sampling and for double sampling. Each of the individual tables constitutes a collection of solutions to the problem of minimizing the over-all amount of inspection. Because each line in the tables covers a range of lot sizes, the AOQL values in the LTPD tables and the LTPD values in the AOQL tables are often conservative.
Note 1—Tables in Annex A1-Annex A4 and parts of the text are reproduced by permission of John R. Wiley and Sons. More extensive tables and discussion of the methods will be found in that text.
The sampling tables based on lot quality protection (LTPD) (the tables in Annex A1 and Annex A2) are perhaps best adapted to conditions where interest centers on each lot separately, for example, where the individual lot tends to retain its identity either from a shipment or a service standpoint. These tables have been found particularly useful in inspections made by the ultimate consumer or a purchasing agent for lots or shipments purchased more or less intermittently.
The sampling tables based on average quality protection (AOQL) (the tables in Annex A3 and Annex A4) are especially adapted for use where interest centers on the average quality of product after inspection rather than on the quality of each individual lot and where inspection is, therefore, intended to serve, if necessary, as a partial screen for defective pieces. The latter point of view has been found particularly helpful, for example, in consumer inspections of continuing purchases of large quantities of a product and in manufacturing process inspections of parts where the inspection lots tend to lose their identity by merger in a common storeroom from which quantities are withdrawn on order as needed.
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SCOPE
1.1 This practice is primarily a statement of principals for the guidance of ASTM technical committees and others in the use of Average Outgoing Quality Limit, AOQL, and Lot Tolerance Percent Defective, LTPD, sampling plans for determining acceptable of lots of product.
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An American National Standard
Designation:E1994–08
Standard Practice for
1
Use of Process Oriented AOQL and LTPD Sampling Plans
This standard is issued under the fixed designation E1994; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
This standard is an abbreviated compilation of the sampling plans presented by H.F. Dodge and
H.G. Romig in their classic development of sampling plans for use with the process associated with
acontinuingsupplyofproducts.ThesocalledAOQLplansprovideameansfordispositionofproduct
whether or not the process is in control as well as incentives for process improvement in terms of
reduced sample size as the process average percent defective is lowered. In addition, so called LTPD
plans are provided for use with individual lots of product, not necessarily associated with a process
stream.
The sampling plans and parts of the text given here are taken from the Wiley Classics Library
Edition of the Dodge-Romig tables (copyright 1998).Additional tables and detailed discussion of the
2
plans, OC curves, and their derivation will be found in that text. The theoretical development of the
,
3 4
Dodge-Roming plans will be found in Volumes 8 and 20 of the Bell System Technical Journal and
5
an amplification of the plans is given in Acceptance Sampling in Quality Control.
1. Scope 3. Terminology
1.1 This practice is primarily a statement of principals for 3.1 Definitions—Terminology E456 provides a more exten-
the guidance of ASTM technical committees and others in the sive list of terms in E11 standards.
use of Average Outgoing Quality Limit, AOQL, and Lot 3.2 lot tolerance percent defective (LTPD)—the percentage
Tolerance Percent Defective, LTPD, sampling plans for deter- of defective units in a batch or lot for which, for purposes of
mining acceptable of lots of product. acceptance sampling, the consumer wishes the probability of
acceptancetoberestrictedtoaspecifiedlowvalue,specifically
2. Referenced Documents
10 % for this practice. This is also referred to by the more
6
2.1 ASTM Standards: general term limiting quality taken at 10 % consumer risk.
E178 Practice for Dealing With Outlying Observations
3.3 average outgoing quality (AOQ)—the average percent
E456 Terminology Relating to Quality and Statistics defective of outgoing product including all accepted lots or
batches,afteranydefectiveunitsfoundinthemarereplacedby
acceptableunits,plusalllotsorbatcheswhicharenotaccepted
1
This practice is under the jurisdiction ofASTM Committee E11 on Quality and
after such lots or batches have been effectively 100 % in-
Statistics and is the direct responsibility of Subcommittee E11.30 on Statistical
spected and all defective units replaced by acceptable units.
Quality Control.
Current edition approved Oct. 1, 2008. Published October 2008. Originally
3.4 average outgoing quality limit (AOQL)—the maximum
approved in 1998. Last previous edition approved in 2003 as E1994 – 98 (2003).
of the AOQs for all possible incoming percentages defective
DOI: 10.1520/E1994-08.
2 for the process, for a given acceptance sampling plan.
Available from John Wiley and Sons, Inc., 605 Third Ave., New York, NY
10158. 3.5 lot quality protection—a type of protection in which
3
Dodge,H.F.andRomig,H.G.,“AMethodofSamplingInspection,” The Bell
there is prescribed some chosen value of limiting percent
System Technical Journal, Vol 8, No. 10, 1924, pp. 613–631.
4 defective in a lot (lot tolerance percent defective, (LTPD)) and
Dodge, H. F. and Romig, H. G., “Single Sampling and Double Sampling
also some chosen value for the probability (called the consum-
Inspection Tables,” The Bell System Technical Journal, Vol 20, No. 1, 1941, pp.
1–61.
er’s risk) of accepting a submitted lot that has a percent
5
Schilling, E. G., Acceptance Sampling in Quality Control, Marcel Dekker Inc.,
defective equal to the lot tolerance percent defective.
NY, 1982, pp. 372–399.
6
3.6 average quality protection—a type of protection in
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM whichthereisprescribedsomechosenvalueofaveragepercent
Standards volume information, refer to the standard’s Document Summary page on
defective in the product after inspection (average outgoing
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1
---------------------- Page: 1 ----------------------
E1994–08
quality limit (AOQL), that shall not be exceeded in the long type of prote
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This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
An American National Standard
Designation:E1994–98 (Reapproved 2003) Designation:E1994–08
Standard Practice for
1
Use of Process Oriented AOQL and LTPD Sampling Plans
This standard is issued under the fixed designation E 1994; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
This standard is an abbreviated compilation of the sampling plans presented by H.F. Dodge and
H.G. Romig in their classic development of sampling plans for use with the process associated with
acontinuingsupplyofproducts.ThesocalledAOQLplansprovideameansfordispositionofproduct
whether or not the process is in control as well as incentives for process improvement in terms of
reduced sample size as the process average percent defective is lowered. In addition, so called LTPD
plans are provided for use with individual lots of product, not necessarily associated with a process
stream.
The sampling plans and parts of the text given here are taken from the Wiley Classics Library
Edition of the Dodge-Romig tables (copyright 1998).Additional tables and detailed discussion of the
2
plans, OC curves, and their derivation will be found in that text. The theoretical development of the
,
3 4
Dodge-Roming plans will be found in Volumes 8 and 20 of the Bell System Technical Journal and
5
an amplification of the plans is given in Acceptance Sampling in Quality Control.
1. Scope
1.1 This practice is primarily a statement of principals for the guidance of ASTM technical committees and others in the use
of Average Outgoing Quality Limit, AOQL, and Lot Tolerance Percent Defective, LTPD, sampling plans for determining
acceptable of lots of product.
2. Referenced Documents
6
2.1 ASTM Standards:
E 178 Practice for Dealing withWith Outlying Observations
E 456 Terminology Relating to Quality and Statistics
3. Terminology
3.1 Definitions— Terminology E 456 provides a more extensive list of terms in E11 standards.
3.2 lot tolerance percent defective (LTPD)— the percentage of defective units in a batch or lot for which, for purposes of
acceptance sampling, the consumer wishes the probability of acceptance to be restricted to a specified low value, specifically 10 %
for this practice. This is also referred to by the more general term limiting quality taken at 10 % consumer risk.
3.2
3.3 average outgoing quality (AOQ)—the average percent defective of outgoing product including all accepted lots or batches,
after any defective units found in them are replaced by acceptable units, plus all lots or batches which are not accepted after such
lots or batches have been effectively 100 % inspected and all defective units replaced by acceptable units.
3.3
3.4 average outgoing quality limit (AOQL)— the maximum of the AOQs for all possible incoming percentages defective for
the process, for a given acceptance sampling plan.
1
This practice is under the jurisdiction of ASTM Committee E11.30 on Data Analysis.
Current edition approved Oct. 1, 2003. Published January 1999.
1
This practice is under the jurisdiction of ASTM Committee E11.30 on Statistical Quality Control.
Current edition approved Oct. 1, 2008. Published October . Originally approved in 1998. Last previous edition approved in 2003 as E 1994–98(2003).
2
Available from John Wiley and Sons, Inc., 605 Third Ave., New York, NY 10158.
3
Dodge, H.F. and Romig, H.G., “A Method of Sampling Inspection,” The Bell System Technical Journal, Vol 8 , No. 10, 1924, pp. 613–631.
4
Dodge, H.F. and Romig, H.G., “Single Sampling and Double Sampling Inspection Tables, The Bell System Technical Journal, Vol 20 , No. 1, 1941, pp. 1–61.
5
Schilling, E.G., “Acceptance Sampling in Quality Control,” Marcel Dekker Inc., NY, 1982, pp. 372–399.
6
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
, Vol 14.02.volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1
---------------------- Page: 1 ----------------------
E1994–08
3.4
3.5 lot quality protection—a type of protection in which there is prescribed some chosen value of limiting percent defective in
a lot (lot tolerance percent defective, (LTPD)) and
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