SIST EN ISO 14253-1:2018

Geometrical product specifications (GPS) - Inspection by measurement of workpieces and measuring equipment - Part 1: Decision rules for proving conformity or nonconformity with specifications (ISO 14253-1:2017)

This document establishes the rules for verifying the conformity or nonconformity with a given
tolerance for a characteristic of a workpiece (or a population of workpieces) or with a given maximum
permissible errors for a metrological characteristic of a measuring equipment, including when the
measured value falls close to the specification limits, taking measurement uncertainty into account.
This document applies to specifications defined in general GPS standards (see ISO 14638), i.e. standards
prepared by ISO/TC 213, including:
— workpiece specifications and population specifications (usually given as an upper specification
limit or a lower specification limit or both);
— measuring equipment specifications (usually given as maximum permissible errors).
This document only applies for characteristics and maximum permissible errors expressed as
quantity values.

Geometrische Produktspezifikationen (GPS) - Prüfung von Werkstücken und Meßgeräten durch Messen - Teil 1: Entscheidungsregeln für den Nachweis von Konformität oder Nichtkonformität mit Spezifikationen (ISO 14253-1:2017)

Dieses Dokument legt Regeln für die Prüfung der Konformität oder Nichtkonformität mit einer vorgegebenen Toleranz für das Merkmal eines Werkstücks (oder eine Population von Werkstücken) oder mit den Grenzwerten für Messabweichungen für ein messtechnisches Merkmal eines Messmittels, auch wenn sich der Messwert unter Berücksichtigung der Messunsicherheit sehr nahe an einem der Grenzwerte der Spezifikation befindet.
Dieses Dokument gilt für Spezifikationen in allgemeinen GPS-Normen (siehe ISO 14638), die vom ISO/TC 213 erarbeitet wurden, einschließlich:
- Spezifikationen für Werkstücke und für die Population von Werkstücken (üblicherweise als eine obere Spezifikationsgrenze oder eine untere Spezifikationsgrenze oder beides angegeben);
- Spezifikationen für Messgeräte (üblicherweise als maximal zulässige Messabweichungen angegeben).
Dieses Dokument gilt nur für Merkmale und maximal zulässige Messabweichungen, die als Größenwerte angegeben werden.

Spécification géométrique des produits (GPS) - Vérification par la mesure des pièces et des équipements de mesure - Partie 1: Règles de décision pour prouver la conformité ou la non-conformité à la spécification (ISO 14253-1:2017)

L'ISO 14253-1 :2017 établit les règles permettant de contrôler la conformité ou la non-conformité à une tolérance donnée pour une caractéristique d'une pièce (ou d'une population de pièces) ou à des erreurs maximales tolérées données pour une caractéristique métrologique d'un équipement de mesure, y compris lorsque la valeur mesurée est proche des limites de spécification, en prenant en compte l'incertitude de mesure.
L'ISO 14253-1 :2017 s'applique aux spécifications définies dans les normes générales GPS (voir l'ISO 14638), c'est-à-dire les normes élaborées par l'ISO/TC 213, comprenant:
-      les spécifications de pièces et les spécifications de population (généralement exprimées sous forme de limite de spécification supérieure, ou de limite de spécification inférieure, ou les deux);
-      les spécifications des équipements de mesure (généralement exprimées sous forme d'erreurs maximales tolérées).
L'ISO 14253-1 :2017 s'applique uniquement aux caractéristiques et aux erreurs maximales tolérées exprimées sous forme de valeurs de grandeurs.

Specifikacija geometrijskih veličin izdelka (GPS) - Preverjanje z merjenjem obdelovancev in z merilno opremo - 1. del: Pravila odločanja za potrjevanje skladnosti ali neskladnosti s specifikacijo (ISO 14253-1:2017)

Ta dokument določa pravila za preverjanje skladnosti ali neskladnosti s podano toleranco za značilnost obdelovanca (ali skupine obdelovancev) ali podanimi največjimi dovoljenimi napakami za meroslovne značilnosti opreme za merjenje, vključno s primeri, ko je izmerjena vrednost blizu omejitev iz specifikacije, pri čemer se upošteva merilna negotovost.
Ta dokument se uporablja za specifikacije, opredeljene v splošnih standardih o specifikaciji geometrijskih veličin proizvoda (glej ISO 14638), tj. standardih, ki jih pripravlja ISO/TC 213, vključno s:
– specifikacijami obdelovanca in populacije (običajno podanimi kot zgornja meja, spodnja meja ali oboje),
– specifikacijami merilne opreme (običajno podanimi kot največje dovoljene napake).
Ta dokument se uporablja za lastnosti in največje dovoljene napake, ki so izražene kot količine/vrednosti.

General Information

• Status: Published
• Public Enquiry End Date: 09-Aug-2016
• Publication Date: 03-Jan-2018
• ICS: 17.040.30 - Measuring instruments
• ICS: 17.040.40 - Geometrical Product Specification (GPS)
• Technical Committee: ISEL - Mechanical elements
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 19-Dec-2017
• Due Date: 23-Feb-2018
• Completion Date: 04-Jan-2018
• Ref Project: EN ISO 14253-1:2017 - Geometrical product specifications (GPS) - Inspection by measurement of workpieces and measuring equipment - Part 1: Decision rules for verifying conformity or nonconformity with specifications (ISO 14253-1:2017)

Relations

• Revised: SIST EN ISO 14253-1:2014 - Geometrical product specifications (GPS) - Inspection by measurement of workpieces and measuring equipment - Part 1: Decision rules for proving conformity or nonconformity with specification (ISO 14253-1:2013)
• Effective Date: 01-Jul-2016
• Replaces: SIST EN ISO 14253-1:2014 - Geometrical product specifications (GPS) - Inspection by measurement of workpieces and measuring equipment - Part 1: Decision rules for proving conformity or nonconformity with specification (ISO 14253-1:2013)
• Effective Date: 13-Dec-2017

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 14253-1:2018
01-februar-2018
1DGRPHãþD
SIST EN ISO 14253-1:2014
6SHFLILNDFLMDJHRPHWULMVNLKYHOLþLQL]GHOND*363UHYHUMDQMH]PHUMHQMHP
REGHORYDQFHYLQ]PHULOQRRSUHPRGHO3UDYLODRGORþDQMD]DSRWUMHYDQMH
VNODGQRVWLDOLQHVNODGQRVWLVVSHFLILNDFLMR,62

Geometrical product specifications (GPS) - Inspection by measurement of workpieces

and measuring equipment - Part 1: Decision rules for proving conformity or
nonconformity with specifications (ISO 14253-1:2017)
Geometrische Produktspezifikationen (GPS) - Prüfung von Werkstücken und
Meßgeräten durch Messen - Teil 1: Entscheidungsregeln für den Nachweis von
Konformität oder Nichtkonformität mit Spezifikationen (ISO 14253-1:2017)

Spécification géométrique des produits (GPS) - Vérification par la mesure des pièces et

des équipements de mesure - Partie 1: Règles de décision pour prouver la conformité ou

la non-conformité à la spécification (ISO 14253-1:2017)
Ta slovenski standard je istoveten z: EN ISO 14253-1:2017
ICS:
17.040.30 Merila Measuring instruments
17.040.40 6SHFLILNDFLMDJHRPHWULMVNLK Geometrical Product
YHOLþLQL]GHOND*36 Specification (GPS)
SIST EN ISO 14253-1:2018 en

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

---------------------- Page: 1 ----------------------
SIST EN ISO 14253-1:2018
---------------------- Page: 2 ----------------------
SIST EN ISO 14253-1:2018
EN ISO 14253-1
EUROPEAN STANDARD
NORME EUROPÉENNE
December 2017
EUROPÄISCHE NORM
ICS 17.040.40 Supersedes EN ISO 14253-1:2013
English Version
Geometrical product specifications (GPS) - Inspection by
measurement of workpieces and measuring equipment -
Part 1: Decision rules for verifying conformity or
nonconformity with specifications (ISO 14253-1:2017)

Spécification géométrique des produits (GPS) - Geometrische Produktspezifikationen (GPS) - Prüfung

Vérification par la mesure des pièces et des von Werkstücken und Messgeräten durch Messen - Teil

équipements de mesure - Partie 1: Règles de décision 1: Entscheidungsregeln für den Nachweis von

pour contrôler la conformité ou la non-conformité à la Konformität oder Nichtkonformität mit Spezifikationen

spécification (ISO 14253-1:2017) (ISO 14253-1:2017)
This European Standard was approved by CEN on 28 September 2017.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this

European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references

concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN

member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by

translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 14253-1:2017 E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN ISO 14253-1:2018
EN ISO 14253-1:2017 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

---------------------- Page: 4 ----------------------
SIST EN ISO 14253-1:2018
EN ISO 14253-1:2017 (E)
European foreword

This document (EN ISO 14253-1:2017) has been prepared by Technical Committee ISO/TC 213

"Dimensional and geometrical product specifications and verification" in collaboration with Technical

Committee CEN/TC 290 “Dimensional and geometrical product specification and verification” the

secretariat of which is held by AFNOR.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by June 2018 and conflicting national standards shall be

withdrawn at the latest by June 2018.

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

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

This document supersedes EN ISO 14253-1:2013.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,

France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,

Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
Endorsement notice

The text of ISO 14253-1:2017 has been approved by CEN as EN ISO 14253-1:2017 without any

modification.
---------------------- Page: 5 ----------------------
SIST EN ISO 14253-1:2018
---------------------- Page: 6 ----------------------
SIST EN ISO 14253-1:2018
INTERNATIONAL ISO
STANDARD 14253-1
Third edition
2017-10
Geometrical product specifications
(GPS) — Inspection by measurement
of workpieces and measuring
equipment —
Part 1:
Decision rules for verifying conformity
or nonconformity with specifications
Spécification géométrique des produits (GPS) — Vérification par la
mesure des pièces et des équipements de mesure —
Partie 1: Règles de décision pour contrôler la conformité ou la non-
conformité à la spécification
Reference number
ISO 14253-1:2017(E)
ISO 2017
---------------------- Page: 7 ----------------------
SIST EN ISO 14253-1:2018
ISO 14253-1:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland

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

or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior

written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of

the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. [phone]
Fax [phone]
[e-mail]
www.iso.org
ii © ISO 2017 – All rights reserved
---------------------- Page: 8 ----------------------
SIST EN ISO 14253-1:2018
ISO 14253-1:2017(E)
Contents Page

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

Introduction ..................................................................................................................................................................................................................................v

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

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

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Default decision rules ..................................................................................................................................................................................... 7

4.1 General ........................................................................................................................................................................................................... 7

4.2 Default conformance probability limit ............................................................................................................................11

4.3 Default nonconformance probability limit ..................................................................................................................11

5 Verifying conformity and nonconformity with specifications ...........................................................................11

5.1 General ........................................................................................................................................................................................................11

5.2 Rule for verifying conformity with specifications .................................................................................................12

5.2.1 General...................................................................................................................................................................................12

5.2.2 Case of normal PDF and default conformance probability limit .........................................12

5.3 Rule for verifying nonconformity with specifications .......................................................................................14

5.3.1 General...................................................................................................................................................................................14

5.3.2 Case of normal PDF and default nonconformance probability limit................................14

5.4 Uncertainty zone ................................................................................................................................................................................15

6 Application in a supplier/customer relationship ...........................................................................................................16

6.1 General ........................................................................................................................................................................................................16

6.2 Supplier verifying conformity .................................................................................................................................................16

6.3 Customer verifying nonconformity ....................................................................................................................................17

Annex A (informative) Relation between the third edition and the second edition ........................................18

Annex B (informative) Relation to the GPS matrix model ...........................................................................................................21

Bibliography .............................................................................................................................................................................................................................23

© ISO 2017 – All rights reserved iii
---------------------- Page: 9 ----------------------
SIST EN ISO 14253-1:2018
ISO 14253-1:2017(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.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

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. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following

URL: www.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 213, Dimensional and geometrical product

specifications and verification, in collaboration with Technical Committee CEN/TC 290, Dimensional and

geometrical product specification and verification.

This third edition cancels and replaces the second edition (ISO 14253-1:2013), which has been

technically revised with the following changes:

— The content applies ISO/IEC Guide 98-4 and gives recommendation for simplification by using

intervals representing the underlying probability. As a consequence, the default coverage factor

k = 2 has been replaced with a default conformance probability of 95 %. This makes the risk constant,

regardless of the relationship between the specification interval and the measurement uncertainty.

See Annex A for additional information.
— Some terminology has been updated.

— The explanation for the population specification modifier has been removed and can now be found

in ISO 18391.
A list of all parts in the ISO 14253 series can be found on the ISO website.
iv © ISO 2017 – All rights reserved
---------------------- Page: 10 ----------------------
SIST EN ISO 14253-1:2018
ISO 14253-1:2017(E)
Introduction

This document is a geometrical product specifications (GPS) standard and is to be regarded as a general

GPS standard (see ISO 14638). It influences the chain link D of all chains of general GPS standards.

The ISO/GPS Matrix model given in ISO 14638 gives an overview of the ISO/GPS system of which this

document is a part. The fundamental rules of ISO/GPS given in ISO 8015 apply to this document and the

default decision rules given in this document apply in ISO/GPS, unless otherwise indicated.

For more detailed information on the relation of this document to other standards and the GPS matrix

model, see Annex B for additional information.

The estimated measurement uncertainty is to be taken into account when verifying conformity or

nonconformity with specification.

The problem arises when a measured value falls close to the upper or lower specification limit. In this

case, verification of conformity or nonconformity with specifications is not possible: the measurement

uncertainty induces a probability that a true value of the characteristic is out of specification even if the

measured value falls inside the specification zone, or is in specification even if the measured value falls

outside.

Therefore, suppliers and customers should agree in advance in a method to resolve any issues that may

arise. This document explains how to define default acceptance and rejection zones (i.e. decision rules)

for verifying conformity or nonconformity with specifications.

It is not the intention of this document to consider any prior knowledge of the possible values of the

measurand(s), e.g. the variability of the measured objects, which may influence the probability of

making the correct decision on verification [in mathematical terms, an a priori unconstrained maximum

entropy distribution (12) is assumed].
© ISO 2017 – All rights reserved v
---------------------- Page: 11 ----------------------
SIST EN ISO 14253-1:2018
---------------------- Page: 12 ----------------------
SIST EN ISO 14253-1:2018
INTERNATIONAL STANDARD ISO 14253-1:2017(E)
Geometrical product specifications (GPS) — Inspection by
measurement of workpieces and measuring equipment —
Part 1:
Decision rules for verifying conformity or nonconformity
with specifications
1 Scope

This document establishes the rules for verifying the conformity or nonconformity with a given

tolerance for a characteristic of a workpiece (or a population of workpieces) or with a given maximum

permissible errors for a metrological characteristic of a measuring equipment, including when the

measured value falls close to the specification limits, taking measurement uncertainty into account.

This document applies to specifications defined in general GPS standards (see ISO 14638), i.e. standards

prepared by ISO/TC 213, including:

— workpiece specifications and population specifications (usually given as an upper specification

limit or a lower specification limit or both);

— measuring equipment specifications (usually given as maximum permissible errors).

This document only applies for characteristics and maximum permissible errors expressed as

quantity values.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements 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 3534-2, Statistics — Vocabulary and symbols — Part 2: Applied statistics
ISO 9000, Quality management systems — Fundamentals and vocabulary

ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in

measurement (GUM:1995)

ISO/IEC Guide 98-4, Uncertainty of measurement — Part 4: Role of measurement uncertainty in conformity

assessment

ISO/IEC Guide 99, International vocabulary of metrology — Basic and general concepts and associated

terms (VIM)
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 3534-2, ISO 9000,

ISO/IEC Guide 98-3, ISO/IEC Guide 98-4 and ISO/IEC Guide 99 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at http://www.iso.org/obp
© ISO 2017 – All rights reserved 1
---------------------- Page: 13 ----------------------
SIST EN ISO 14253-1:2018
ISO 14253-1:2017(E)
— IEC Electropedia: available at http://www.electropedia.org/
NOTE 1 “Probability density function (PDF)” is defined in ISO 3534-1.

NOTE 2 “Specification limit”, “upper specification limit (USL)”, “lower specification limit (LSL)”, “specified

tolerance” and “population” are defined in ISO 3534-2.

NOTE 3 “Maximum permissible measurement error”, “measurement uncertainty”, “standard measurement

uncertainty”, “combined standard measurement uncertainty”, “coverage interval” and “coverage probability” are

defined in ISO/IEC Guide 99.

NOTE 4 “Acceptance limit”, “acceptance interval”, “rejection interval”, “conformance probability” and “guard

band” are defined in ISO/IEC Guide 98-4.
NOTE 5 “Conformity” and “nonconformity” are defined in ISO 9000.

NOTE 6 For the purposes of this document, “characteristic” is used to express either a workpiece

characteristic, a workpiece population characteristic, or a metrological characteristic of measuring equipment.

Because conformity assessment involves measurement, these characteristics are also referred to as measurands.

3.1
specification zone

interval of values, of the workpiece characteristic or population characteristic or the maximum

permissible error (MPE) of a metrological characteristic of a measuring equipment, fulfilling the

specification

Note 1 to entry: A specification refers to or includes drawings, patterns or other relevant documents.

3.2
conformance probability limit
agreed minimum value of conformance probability when verifying conformity

Note 1 to entry: The conformance probability limit effectively sets the criterion for acceptance when verifying

conformity.

Note 2 to entry: A conformance probability limit of p corresponds to a risk of false acceptance less than or equal

to (1 − p).
3.3
default conformance probability limit
conformance probability limit (3.2) set by this document as default
3.4
lower nonconformance probability

probability that a value of a characteristic is below the lower specification limit

Note 1 to entry: A lower nonconformance probability exists only if a lower specification limit exists.

Note 2 to entry: Conformance probability, lower nonconformance probability and upper nonconformance

probability sum up to unity.
3.5
upper nonconformance probability

probability that a value of a characteristic is above the upper specification limit

Note 1 to entry: An upper nonconformance probability exists only if an upper specification limit exists.

Note 2 to entry: Conformance probability, lower nonconformance probability and upper nonconformance

probability sum up to unity.
2 © ISO 2017 – All rights reserved
---------------------- Page: 14 ----------------------
SIST EN ISO 14253-1:2018
ISO 14253-1:2017(E)
3.6
nonconformance probability limit

agreed minimum value of either the upper nonconformance probability (3.5) or the lower nonconformance

probability (3.4) when verifying nonconformity

Note 1 to entry: The nonconformance probability limit effectively sets the criterion for rejection when verifying

nonconformity.

Note 2 to entry: A nonconformance probability limit of p implies a risk of false rejection not exceeding (1 − p).

3.7
default nonconformance probability limit
nonconformance probability limit (3.6) set by this document as default
3.8
acceptance zone
set of one or more acceptance intervals
3.9
default acceptance zone
acceptance zone (3.8) based on the default conformance probability limit (3.3)
Note 1 to entry: See Figure 1.
© ISO 2017 – All rights reserved 3
---------------------- Page: 15 ----------------------
SIST EN ISO 14253-1:2018
ISO 14253-1:2017(E)

a) Specification defined only by a lower b) Specification defined only by an upper

specification limit specification limit
c) Specification defined by a lower and an upper specification limit
Key
1 specification zone
2 acceptance limits
3 acceptance zone
4 rejection zone
5 guard band g at lower specification limit
6 guard band g at upper specification limit
Y value of characteristic
LSL lower specification limit
USL upper specification limit

NOTE In most cases, the probability density function (PDF) associated with the measured value of the

characteristic is considered to be symmetrical, so that g , g have the same width.

UA LA
Figure 1 — Acceptance zone and rejection zone when verifying conformity
3.10
rejection zone
set of one or more rejection intervals

Note 1 to entry: The rejection zone is the complement to the acceptance zone (3.8).

3.11
default rejection zone

rejection zone (3.10) based on the default nonconformance probability limit (3.7).

Note 1 to entry: See Figure 2.
4 © ISO 2017 – All rights reserved
---------------------- Page: 16 ----------------------
SIST EN ISO 14253-1:2018
ISO 14253-1:2017(E)

a) Specification defined only by a lower b) Specification defined only by an upper

specification limit specification limit
c) Specification defined by a lower and an upper specification limit
Key
1 specification zone
2 acceptance limits
3 acceptance zone
4 rejection zone
7 guard band g at lower specification limit
8 guard band g at upper specification limit
Y value of characteristic
LSL lower specification limit
USL upper specification limit

NOTE In most cases, the probability density function (PDF) associated with the measured value of the

characteristic is considered to be symmetrical, so that g , g have the same width.

UR LR
Figure 2 — Rejection zone and acceptance zone when verifying nonconformity
3.12
uncertainty zone

set of interval(s) close to the specification limit(s) where neither conformity can be verified according

to the conformance probability limit (3.2) nor nonconformity can be verified according to the

nonconformance probability limit (3.6)

Note 1 to entry: The uncertainty zone is located about the specification limit (unilateral specification) or

specification limits (bilateral specification).

Note 2 to entry: The uncertainty zone on the upper and lower side of a specification limit may be of different

magnitudes.

Note 3 to entry: When verifying conformity, the uncertainty zone is part of the rejection zone (3.10) and not part

of the acceptance zone (3.8).
© ISO 2017 – All rights reserved 5
---------------------- Page: 17 ----------------------
SIST EN ISO 14253-1:2018
ISO 14253-1:2017(E)

Note 4 to entry: When verifying nonconformity, the uncertainty zone is part of the acceptance zone (3.8) and not

part of the rejection zone (3.10).
Note 5 to entry: See Figure 3, Figure 4, Figure 5 and Figure 6.

a) Specification defined only by a lower b) Specification defined only by an upper

specification limit specification limit
c) Specification defined by a lower and an upper specification limit
Key
1 specification zone
2A acceptance limits for verifying conformity
2R acceptance limits for verifying nonconformity
5 guard band g at lower specification limit for verifying conformity
6 guard band g at upper specification limit for verifying conformity
7 guard band g at lower specification limit for verifying nonconformity
8 guard band g at upper specification limit for verifying nonconformity
9 uncertainty zone
Y value of characteristic
LSL lower specification limit
USL upper specification limit

NOTE 1 Figure 3 c) could be seen as a combination of Figure 3 a) and Figure 3 b).

NOTE 2 In most cases, the probability density function (PDF) associated with the measured value of the

characteristic is considered to be symmetrical, so that g , g and g , g have the same width.

UA LA UR LR
Figure 3 — Uncertainty zone
6 © ISO 2017 – All rights reserved
---------------------- Page: 18 ----------------------
SIST EN ISO 14253-1:2018
ISO 14253-1:2017(E)
4 Default decision rules
4.1 General

A given specification (workpiece(s) characteristic with LSL and/or USL) is expressed on the drawing

and the respective chain of standards (see ISO 14638) or by the detailed description of the metrological

characteristic of the measurement equipment (e.g. in a standard) and the maximum permissible error

(MPE) of the indicated value.

Any measurement is affected by measurement uncertainty: the true value cannot be known exactly

and is expected to fall, with a predefined coverage probability, within a coverage interval.

NOTE 1 For guidance on how to estimate the measurement uncertainty, follow GUM or ISO 14253-2.

NOTE 2 The uncertainty of the estimate of a workpiece characteristic is different from the uncertainty of

the estimate of the population characteristic (e.g. the uncertainty of an individual value is different from the

uncertainty of an average value).

The central tendency and dispersion of values that can be reasonably attributed to the measurand are

often modelled with a probability density function (PDF).

Often, the PDF is assumed to be Gaussian (normally distributed). In this case, a coverage probability of

95 % corresponds to a coverage factor k = 1,96, typically approximated to k = 2. It is common practice to

assume symmetrical coverage intervals about the measured values; however, asymmetric intervals are

also possible, which are acceptable, as long as the coverage probability is met.

As measured values include uncertainty, any decision based on them is subject to a risk of being false. The

conformance probability is the probability that the true value falls inside the specification zone. Setting

a decision rule such that an item is accepted if the conformance probability is above a conformance

probability limit (e.g. 95 %) effectively confines the risk of false decision to the complement of such

conformance probability limit (e.g. 5 %).

Conformance probability should not be confused with coverage probability; see Clause 3.

Guard bands protect from incorrect decisions based on uncertain measured values close to the

specification limits.

The guard bands are fully determined by the PDF of the result of the measurement and the agreed

probability limit.

The acceptance zone for guarded acceptance is determined by reducing the specification zone of a

workpiece or population characteristic or the maximum permissible error of a measuring equipment

characteristic by the guard bands at each specification limit; see Figure 1. The figure also shows the rule

for unilateral characteristics. Conformity is verified if
...