1、BS ISO 22514-4:2016Statistical methods in processmanagement Capability andperformancePart 4: Process capability estimates andperformance measuresBSI Standards PublicationWB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06BS ISO 22514-4:2016 BRITISH STANDARDNational forewordThis British Standard
2、 is the UK implementation of ISO 22514-4:2016.It supersedes PD ISO/TR 22514-4:2007 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee SS/4, Statistical Process Management.A list of organizations represented on this committee can beobtained on request to it
3、s secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2016. Published by BSI StandardsLimited 2016ISBN 978 0 580 88272 2ICS 03.120.30Compliance with a British Standard ca
4、nnot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 31 August 2016.Amendments issued since publicationDate Text affectedBS ISO 22514-4:2016 ISO 2016Statistical methods in process management Capability and
5、 performance Part 4: Process capability estimates and performance measuresMthodes statistiques dans la gestion de processus Aptitude et performance Partie 4: Estimations de laptitude de processus et mesures de performanceINTERNATIONAL STANDARDISO22514-4First edition2016-08-01Reference numberISO 2251
6、4-4:2016(E)BS ISO 22514-4:2016ISO 22514-4:2016(E)ii ISO 2016 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2016, Published in SwitzerlandAll rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic
7、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 ISOs member body in the country of the requester.ISO copyright officeCh. de Blandonnet 8 CP 401CH-1214 Vernier, Gene
8、va, SwitzerlandTel. +41 22 749 01 11Fax +41 22 749 09 47copyrightiso.orgwww.iso.orgBS ISO 22514-4:2016ISO 22514-4:2016(E)Foreword vIntroduction vi1 Scope . 12 Symbols and abbreviated terms . 12.1 Symbols . 12.2 Abbreviated terms . 33 Basic concepts used for process capability and performance 33.1 Ge
9、neral . 33.2 Location . 33.3 Dispersion . 33.3.1 Inherent dispersion . 33.3.2 Total dispersion 33.3.3 Short-term dispersion . 33.4 Mean square error (MSE) 43.5 Reference limits 43.6 Reference interval (also known as process spread) . 44 Capability . 44.1 General . 44.2 Process capability . 64.2.1 No
10、rmal distribution 64.2.2 Non-normal distribution. 74.3 Process location . 74.4 Process capability indices for measured data 84.4.1 General 84.4.2 Cpindex (for the normal distribution) 94.4.3 Cpkindex (for the normal distribution) 104.4.4 Cpkindex for unilateral tolerances 104.5 Process capability in
11、dices for measured data (non-normal) .104.5.1 General. 104.5.2 Probability paper method . 114.5.3 Pearson curves method . 114.5.4 Distribution identification method .124.6 Alternative method for describing and calculating process capability estimates .124.7 Other capability measures for continuous d
12、ata 134.7.1 Process capability fraction (PCF) .134.7.2 Indices when the specification limit is one-sided or no specification limit is given .134.8 Assessment of proportion out-of-specification (normal distribution) .155 Performance .165.1 General 165.2 Process performance indices for measured data (
13、normal distribution) .165.2.1 Ppindex . 165.2.2 Ppkindex 175.3 Process performance indices for measured data (non-normal distribution) .175.3.1 General. 175.3.2 Probability paper method . 175.3.3 Pearson curves method . 185.3.4 Distribution identification method .185.4 Other performance indices for
14、measured data 185.5 Assessment of proportion out-of-specification for a normal distribution of the total distribution 186 Reporting process capability and performance indices 19 ISO 2016 All rights reserved iiiContents PageBS ISO 22514-4:2016ISO 22514-4:2016(E)Annex A (informative) Estimating standa
15、rd deviations 21Annex B (informative) Estimating capability and performance measures using Pearson curves Procedure and example .23Annex C (informative) Distribution identification 37Annex D (informative) Confidence intervals .42Bibliography .44iv ISO 2016 All rights reservedBS ISO 22514-4:2016ISO 2
16、2514-4:2016(E)ForewordISO (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
17、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) o
18、n 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
19、. 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 an
20、y 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 us
21、ers and does not constitute an endorsement.For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword - Supplement
22、ary information.The committee responsible for this document is Technical Committee ISO/TC 69, Applications of statistical methods, Subcommittee SC 4, Applications of statistical methods in process management.This first edition of ISO 22514-4 cancels and replaces ISO/TR 22514-4:2007, which has been t
23、echnically revised.ISO 22514 consists of the following parts, under the general title Statistical methods in process management Capability and performance: Part 1: General principles and concepts Part 2: Process capability and performance of time-dependent process models Part 3: Machine performance
24、studies for measured data on discrete parts Part 4: Process capability estimates and performance measures Part 5: Process capability estimates and performance for attributive characteristics Part 6: Process capability statistics for characteristics following a multivariate normal distribution Part 7
25、: Capability of measurement processes Part 8: Machine performance of a multi-state production process ISO 2016 All rights reserved vBS ISO 22514-4:2016ISO 22514-4:2016(E)IntroductionMany organizations have embarked upon a continuous improvement strategy. To comply with such a strategy, any organizat
26、ion will need to evaluate the capability and performance of its key processes. The methods described in this part of ISO 22514 are intended to assist any management in this respect. These evaluations need to be constantly reviewed by the management so that actions compatible with continuous improvem
27、ent can be taken when required.The content of this part of ISO 22514 has been subject to large shifts of opinion during recent times. The most fundamental shift has been to philosophically separate what is named in this part of ISO 22514 as capability conditions from performance conditions, the prim
28、ary difference being whether statistical stability has been obtained (capability) or not (performance). This naturally leads onto the two sets of indices that are to be found in their relevant clauses. It has become necessary to draw a firm distinction between these since it has been observed in the
29、 industry that companies have been deceived about their true capability position due to inappropriate indices being calculated and published.The progression of this part of ISO 22514 is from the general condition to the specific and this approach leads to general formulae being presented before thei
30、r more usual, but specific manifestations.There exist numerous references that describe the importance of understanding the processes at work within any organization, be it a manufacturing process or an information handling process. As organizations compete for sales with each other, it has become i
31、ncreasingly apparent that it is not only the price paid for a product or service that matters so much, but also what costs will be incurred by the purchaser from using such a product or service. The objective for any supplier is to continually reduce variability and not to just satisfy specification
32、.Continual improvement leads to reductions in the costs of failure and assists in the drive for survival in an increasingly more competitive world. There will also be savings in appraisal costs for as variation is reduced, the need to inspect product might disappear or the frequency of sampling migh
33、t be reduced.Process capability and performance evaluations are necessary to enable organizations to assess the capability and performance of their suppliers. Those organizations will find the indices contained within this part of ISO 22514 useful in this endeavour.Quantifying the variation present
34、within a process enables judgement of its suitability and ability to meet some given requirement. The following paragraphs and clauses provide an outline of the philosophy required to be understood to determine the capability or performance of any process.All processes will be subject to certain inh
35、erent variability. This part of ISO 22514 does not attempt to explain what is meant by inherent variation, why it exists, where it comes from nor how it affects a process. This part of ISO 22514 starts from the premise that it exists and is stable.Process owners should endeavour to understand the so
36、urces of variation in their processes. Methods such as flowcharting the process and identifying the inputs and outputs from a process assist in identification of these variations together with the appropriate use of cause and effect (fishbone) diagrams.It is important for the user of this part of IS
37、O 22514 to appreciate that variations exist that will be of a short-term nature, as well as those that will be of a long-term nature and that capability determinations using only the short-term variation might be greatly different to those which have used the long-term variability.When considering s
38、hort-term variation, a study that uses only the shortest-term variation, sometimes known as a machine study and described in ISO 22514-3, might be carried out. The method required to carry out such a study will be outside the scope of this part of ISO 22514; however, it should be noted that such stu
39、dies are important and useful.It should be noted that where the capability indices given in this part of ISO 22514 are computed, they only form point estimates of their true values. It is therefore recommended that, wherever possible, the vi ISO 2016 All rights reservedBS ISO 22514-4:2016ISO 22514-4
40、:2016(E)indices confidence intervals are computed and reported. This part of ISO 22514 describes methods by which these can be computed. ISO 2016 All rights reserved viiBS ISO 22514-4:2016BS ISO 22514-4:2016Statistical methods in process management Capability and performance Part 4: Process capabili
41、ty estimates and performance measures1 ScopeThis part of ISO 22514 describes process capability and performance measures that are commonly used.2 Symbols and abbreviated terms2.1 SymbolsIn addition to the symbols listed below, some symbols are defined where they are used within the text. fraction or
42、 proportion shape parameter in a Weibull distribution2coefficient of kurtosisc4constant based on subgroup size, n (see ISO 7870-2)Cpprocess capability indexCpkminimum process capability indexCLpklower process capability indexCUpkupper process capability indexCpmalternative process capability indexCR
43、process capability fraction (PCF)d2constant based on subgroup size, n (see ISO 7870-2)e Eulerss number (approximately 2,718), mathematical constant distribution function of the standard normal distribution location parameter in a Weibull distribution1coefficient of skewnessm number of subgroupsKl, K
44、umultipliers for estimating the confidence limits for a process capability indexL lower specification limitINTERNATIONAL STANDARD ISO 22514-4:2016(E) ISO 2016 All rights reserved 1BS ISO 22514-4:2016ISO 22514-4:2016(E)P0,135 %lower 0,135 % percentile location of the process; population mean valueN t
45、otal sample sizen number of values or subgroup size (for a control chart)P % percentilepLlower fraction nonconformingPpprocess performance indexPpkminimum process performance indexPLpklower process performance indexPUpkupper process performance indexpttotal fraction nonconformingpUupper fraction non
46、conformingP99,865 %upper 99,865 % percentile geometric constantQkprocess variation index parameter required for the Rayleigh distributionRaverage subgroup rangeS standard deviation, sample statisticStstandard deviation, with the subscript t indicating totalSaverage sample standard deviationSjobserve
47、d sample standard deviation of the jthsubgroup standard deviation, populationtestimated standard deviation, totalT target valueU upper specification limitX % % percentileXiithvalue in a sampleXarithmetic mean value, sampleXarithmetic mean, of a number of sample arithmetic means2 ISO 2016 All rights
48、reservedBS ISO 22514-4:2016ISO 22514-4:2016(E) scale parameter in a Weibull distributionY1, Y2values read from a graphzquantile of the standardized normal distribution from to 2.2 Abbreviated termsMSE mean square errorPCF process capability fractionPCI process capability index3 Basic concepts used f
49、or process capability and performance3.1 GeneralThe measures referred to in 4.2 to 4.6 refer only to measured data. They are unsuitable for count or attributes data and information concerning the expression of measures for such data will be found in ISO 22514-5.3.2 LocationThe characterization of location is the mean, , or the median, X50 %. Although for symmetric distributions the mean is the most natural selection, with non-symmetric distributions the median is the preferred selection.3.3 Dispersion3.3.
