BS 6001-5-2002 Sampling procedures for inspection by attributes - Procedures for assessment of declared quality levels《按属性检验的取样规程 申报质量等级的评定规程》.pdf

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1、BRITISH STANDARD BS 6001-5:2002 Sampling procedures for inspection by attributes Part 5: Procedures for assessment of declared quality levels ICS 03.120.30 BS 6001-5:2002 This British Standard, having been prepared under the direction of the Management Systems Sector Policy and Strategy Committee, w

2、as published under the authority of the Standards Policy and Strategy Committee on 1 November 2002 BSI 1 November 2002 ISBN 0 580 40648 2 National foreword This British Standard reproduces verbatim ISO 2859-4:2002 and implements it as the UK national standard. It supersedes BS 6001-5:2000 which is w

3、ithdrawn. The UK participation in its preparation was entrusted to Technical Committee SS/5, Acceptance sampling schemes, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which i

4、mplement international publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not pu

5、rport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European commit

6、tee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the ISO title page, pages ii to

7、v, a blank page, pages 1 to 12, an inside back cover and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date CommentsINTERNATIONAL STANDARD ISO 2859-4 Second edition 2002-08-01 Reference number

8、 ISO 2859-4:2002(E) Sampling procedures for inspection by attributes Part 4: Procedures for assessment of declared quality levels Rgles dchantillonnage pour les contrles par attributs Partie 4: Procdures pour lvaluation des niveaux dclars de qualitBS60015:2002BS60015:2002iiOSI -95822002:4)E( ISO 200

9、2 r llAithgs reservde iii Contents Page 1 Scope . 1 2 Normative references . 2 3 Terms, definitions, symbols and abbreviations . 2 4 Principles 3 5 Declared quality level (DQL) . 4 6 Sampling plans . 4 7 Operating a sampling plan 6 8 Further information . 7 Annex A Examples of use of the procedures

10、11 A.1 Example 1 . 11 A.2 Example 2 . 11 A.3 Example 3 . 11 BS60015:2002iiiISO -95822:4)E(200 vi ISO 2002 Ar llithgr seresvde Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing Internatio

11、nal 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

12、, 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 3. Draft International Standards

13、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 part of ISO 2859 may be the sub

14、ject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. International Standard ISO 2859-4 was prepared by Technical Committee ISO/TC 69, Applications of statistical methods, Subcommittee SC 5, Acceptance sampling. This second edition cancels and replac

15、es the first edition (ISO 2859-4:1999), which has been technically revised. ISO 2859 consists of the following parts, under the general title Sampling procedures for inspection by attributes: Part 0: Introduction to the ISO 2859 attribute sampling system Part 1: Sampling schemes indexed by acceptanc

16、e 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 Annex A of this part of ISO 2859 is for information only. BS60015:2002

17、ivOSI -95822002:4)E( ISO 2002 r llAithgs reservde v Introduction The procedures in this part of ISO 2859 differ in their scope from the procedures in ISO 2859 Parts 1 to 3. The system of acceptance sampling procedures that are specified in ISO 2859 Parts 1 to 3 are intended to be used in bilateral a

18、greements between two parties. The acceptance sampling procedures are intended to be used as simple, pragmatic rules for releasing product after inspection of only a limited sample of a consignment, and therefore the procedures do not make reference (either explicitly or implicitly) to any formally

19、declared quality level. Under acceptance sampling there is no sharp borderline between quality levels that should be considered acceptable and qualities that should be rejected by the procedure. For the procedures in ISO 2859-1 the two parties agree upon some acceptance quality limit (AQL) which is

20、the worst tolerable process average when a continuing series of lots is submitted. The switching rules and the sampling schemes in ISO 2859-1 are designed to encourage the suppliers to have process averages consistently better than the AQL selected. In order to keep sample sizes moderate, the protec

21、tion against accepting individual lots of inferior quality may be less than that provided by sampling plans targeted for sentencing individual lots. The procedures in ISO 2859-2, on the contrary, are designed to provide good protection against accepting individual lots of inferior quality (LQ), but

22、at the expense of a possible high risk of not accepting lots of qualities that both parties actually would consider to be acceptable. Procedures in ISO 2859 Parts 1 to 3 are well suited for acceptance sampling purposes, but they should not be used in reviews, audits, etc. to verify a quality that ha

23、s been declared for some entity. The main reason is that the procedures have been indexed in terms of quality levels that are relevant solely for the pragmatic purposes of acceptance sampling, and the various risks have been balanced accordingly. The procedures in this part of ISO 2859 have been dev

24、eloped as a response to the growing need for sampling procedures suitable for formal, systematic inspections such as reviews or audits. When performing such a formal inspection, it is necessary for the authority to consider the risk of reaching an incorrect conclusion, and to take this risk into acc

25、ount in planning and executing the review/audit/testing, etc. This part of ISO 2859 provides guidance and rules to assist the user in taking this risk into account in an informed manner. The rules in this part of ISO 2859 have been devised such that there is only a small, limited risk of contradicti

26、ng the declared quality level when in fact the actual level conforms to the declared level. If it were also desired that there should be a similarly small risk of not contradicting the declared quality level when in fact the actual quality level does not conform to the declared quality level, then i

27、t would be necessary to investigate a rather large sample. Therefore, in order to obtain the benefit of a moderate sample size, the procedures in this part of ISO 2859 have been devised in such a way that they allow a somewhat higher risk of failing to contradict the declared quality level when in f

28、act the actual quality level does not conform to the declared quality level. The wording of the result of the assessment should reflect this unbalance between the risks of reaching incorrect conclusions. When the sample result contradicts the declared quality level there is strong evidence of noncon

29、formance to the declared quality level. When the sample result does not contradict the declared quality level, this should be understood as “we have not, in this limited sample, found strong evidence of nonconformance to the declared quality level”. BS60015:2002vANRETNIITOTS LANDNADRA OSI -95822002:

30、4)E( ISO 2002 r llAithgs reservde 1 Sampling procedures for inspection by attributes Part 4: Procedures for assessment of declared quality levels 1 Scope This part of ISO 2859 establishes sampling plans and procedures that can be used to assess whether the quality level of an entity (lot, process, e

31、tc) conforms to a declared value. The sampling plans have been devised so as to obtain a risk of less than of contradicting a correct declared quality level. The risk is of failing to contradict an incorrect declared quality level which is related to the limiting quality ratio (see clause 4). Sampli

32、ng plans are provided corresponding to three levels of discriminatory ability. In contrast to the procedures in the other parts of ISO 2859, the procedures in this part of ISO 2859 are not applicable to acceptance assessment of lots. Generally, the balancing of the risks of reaching incorrect conclu

33、sions in assessment procedures will differ from the balancing in the procedures for acceptance sampling. This part of ISO 2859 may be used for various forms of quality inspection in situations where objective evidence of conformity to some declared quality level is to be provided by means of inspect

34、ion of a sample. The procedures are applicable to entities such as lots, process output, etc. that allow random samples of individual items to be taken from the entity. The sampling plans provided in this part of ISO 2859 are applicable, but not limited, to inspection of a variety of products such a

35、s end items; components and raw materials; operations; materials in process; supplies in storage; maintenance operations; data or records; administrative procedures. The procedures are primarily intended to be used when the quantity of interest is the number or fraction of nonconforming items for wh

36、ich the inspected items are classified as conforming or nonconforming. With minor changes, the procedures may also be used when the quantity of interest is the number of nonconformities or number of nonconformities per item. The necessary changes are: replacement of “number of nonconforming items” b

37、y “number of nonconformities”; replacement of “percent nonconforming items” by “nonconformities per 100 items”. In this case the values given in Tables 2 to 7 are only approximations. 5 % 10 % BS60015:20021ISO -95822:4)E(200 2 ISO 2002 Ar llithgr seresvde 2 Normative references The following normati

38、ve documents contain provisions which, through reference in this text, constitute provisions of this part of ISO 2859. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this part of ISO 2859 are encouraged

39、 to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 3534-1:

40、1993, Statistics Vocabulary and symbols Part 1: Probability and general statistical terms ISO 3534-2:1993, Statistics Vocabulary and symbols Part 2: Statistical quality control ISO 9000:2000, Quality management systems Fundamentals and vocabulary 3 Terms, definitions, symbols and abbreviations 3.1 T

41、erms and definitions For the purposes of this part of ISO 2859, the terms and definitions given in ISO 3534-1, ISO 3534-2 and ISO 9000 and the following apply. 3.1.1 limiting number of nonconforming items largest number of nonconforming items (or nonconformities) found in the sample from the entity

42、under investigation that does not lead to contradiction of the declared quality level 3.1.2 quality ratio ratio of the actual to the declared quality level of the entity under investigation 3.1.3 limiting quality ratio LQR value of the quality ratio that is limited to a small risk ( in this part of

43、ISO 2859) of failing to contradict an incorrect declared quality level 3.2 Symbols and abbreviated terms The symbols and abbreviated terms used in this part of ISO 2859 are as follows: DQL Declared quality level Limiting number of nonconforming items in the sample LQR Limiting quality ratio Sample s

44、ize L 10 % L n BS60015:20022OSI -95822002:4)E( ISO 2002 r llAithgs reservde 3 4 Principles In any assessment procedure based on sampling there will be an inherent uncertainty due to possible sampling fluctuations. The procedures in this part of ISO 2859 have been conceived so as to lead to contradic

45、tion of the declared quality level only when there is sufficient evidence to support a conclusion that the actual quality is poorer than the declared quality level. The procedures have been devised in such a way that when the actual quality level is equal to or better than the declared quality level

46、, the risk is less than of contradicting the declared value. Consequently, when the actual quality level is worse than the declared quality level, there is a risk that the procedures will fail to contradict an incorrect declared quality level. This risk depends on the value of the quality ratio, i.e

47、. the ratio between the actual and the declared quality level. The limiting quality ratio, LQR, is introduced to denote the highest quality ratio considered tolerable. When the actual quality level is LQR times worse than the declared quality level, the procedures in this part of ISO 2859 have a ris

48、k ofof failing to contradict the declared quality level (corresponding to a probability of contradicting the incorrect declared quality level). Three LQR levels I, II and III are considered. Details of the three LQR levels provided in this part of ISO 2859 are given in 6.1. The sampling plans provid

49、ed in this part of ISO 2859 are indexed by the limiting quality ratio (LQR) level and the declared quality level (DQL) and are provided in Table 1. Table 1 Master table of sampling plans DQL LQR level I LQR level II LQR level III % nonconforming items 0,010 3 150 1 bb 0,015 2 000 1 bb 0,025 1 250 1 3 150 2 b 0,040 800 1 2 000 2 3 150 3 0,065 500 1 1 250 2 2 000 3 0,100 315 1 800 2 1 250 3 0 , 1 5 02 0 015 0 028 0 03 0 ,