1、BRITISH STANDARD BS 6002-3:2005 Sampling procedures for inspection by variables Part 3: Guide to double sampling schemes indexed by acceptance quality limit (AQL) for lot-by-lot inspection ICS 03.120.30 BS 6002-3:2005 This British Standard, was published under the authority of the Standards Policy a
2、nd Strategy Committee on 31 March 2005 BSI 31 March 2005 The following BSI references relate to the work on this British Standard Committee reference SS/5 Draft for comment 03/102300 DC ISBN 0 580 45424 X Committees responsible for this British Standard The preparation of this British Standard was e
3、ntrusted to Technical Committee SS/5, Acceptance sampling schemes, upon which the following bodies were represented: Association for Road Traffic Safety and Management British Measurement and Testing Association City University, London Clay Pipe Development Association Limited Institute of Metal Fin
4、ishing Institute of Quality Assurance MoD UK Defence Standardization Amendments issued since publication Amd. No. Date CommentBS 6002-3:2005 BSI 31 March 2005 i Contents Page Committees responsible Inside front cover Foreword v Introduction 1 1S c o p e 1 2 Normative references 2 3T e r m s a n d d
5、e f i n i t i o n s 2 4 Symbols and abbreviations 5 5 Acceptance quality limit (AQL) 6 6 Switching rules for normal, tightened and reduced inspection 7 7 Relation to BS 6001-1 8 8 Limiting quality protection 9 9 Planning 9 10 Choice between variables and attributes 10 11 Choice of method 10 12 Choic
6、e between single and double sampling plans 10 13 Choice of inspection level and AQL 11 14 Choice of sampling scheme 11 15 Preliminary operations 12 16 Standard univariate “s” method procedures 12 17 Standard univariate “ ” method procedures 21 18 Procedure during continuing inspection 27 19 Normalit
7、y and outliers 27 20 Records 28 21 Operation of switching rules 28 22 Discontinuation and resumption of inspection 29 23 Switching between the “s” and “ ” methods 29 Annex A (informative) Standard multivariate “s” method procedures for double sampling with independent quality characteristics 65 Anne
8、x B (informative) Standard multivariate “ ” method procedures for double sampling with independent quality characteristics 66 Annex C (informative) Standard multivariate combined “s” and “ ” method procedures for double sampling with independent quality characteristics 68 Annex D (informative) Locat
9、ion of text on key features 69 Annex E (normative) Estimating the process fraction nonconforming 70 Annex F informative) Form k “s” method single sampling plans matched to the corresponding single sampling plans by attributes 76 Annex G (informative) Form k “ ” method single sampling plans matched t
10、o the corresponding single sampling plans by attributes 79 Annex H (informative) Average sample numbers for double sampling by variables: “s” method 82 Annex I (informative) Producers risks for the “s” method 85 Annex J (informative) Tabulated operating characteristics for double sampling plans with
11、 known process standard deviation 88 Annex K (informative) Ratios of ASNs of double sampling plans under normal inspection to the sample size of the corresponding single sampling plan by variables 95 Annex L (informative) Ratios of the ASNs of double sampling plans by variables to the ASNs of corres
12、ponding plans by attributes 97 Bibliography 101BS 6002-3:2005 ii BSI 31 March 2005 Page Chart A Sample size code letters of standard double sampling plans for specified qualities at 95 % and 50 % probabilities of acceptance 50 Chart C Operating characteristic curves for double sampling plans, normal
13、 inspection Sample size code letter C, “s” method 51 Chart D Operating characteristic curves for double sampling plans, normal inspection Sample size code letter D, “s” method 52 Chart E Operating characteristic curves for double sampling plans, normal inspection Sample size code letter E, “s” metho
14、d 53 Chart F Operating characteristic curves for double sampling plans, normal inspection Sample size code letter F, “s” method 54 Chart G Operating characteristic curves for double sampling plans, normal inspection Sample size code letter G, “s” method 55 Chart H Operating characteristic curves for
15、 double sampling plans, normal inspection Sample size code letter H, “s” method 56 Chart J Operating characteristic curves for double sampling plans, normal inspection Sample size code letter J, “s” method 57 Chart K Operating characteristic curves for double sampling plans, normal inspection Sample
16、 size code letter K, “s” method 58 Chart L Operating characteristic curves for double sampling plans, normal inspection Sample size code letter L, “s” method 59 Chart M Operating characteristic curves for double sampling plans, normal inspection Sample size code letter M, “s” method 60 Chart N Opera
17、ting characteristic curves for double sampling plans, normal inspection Sample size code letter N, “s” method 61 Chart P Operating characteristic curves for double sampling plans, normal inspection Sample size code letter P, “s” method 62 Chart Q Operating characteristic curves for double sampling p
18、lans, normal inspection Sample size code letter Q, “s” method 63 Chart R Operating characteristic curves for double sampling plans, normal inspection Sample size code letter R, “s” method 64 Table 1 Sample size code letters and inspection levels 29 Table 2.1 Form k double sampling plans for normal i
19、nspection (master table) “s”m et h o d 3 0 Table 2.2 Form k double sampling plans for tightened inspection (master table) “s” method 31 Table 2.3 Form k double sampling plans for reduced inspection (master table) “s” method 32 Table 3.1 Form k double sampling plans for normal inspection (master tabl
20、e) “ ” method 33 Table 3.2 Form k double sampling plans for tightened inspection (master table) “ ”met hod 34 Table 3.3 Form k double sampling plans for reduced inspection (master table) “ ”met hod 35 Table 4.1 Values of f sfor maximum sample standard deviation (MSSD) for combined control of double
21、specification limits Normal inspection, “s” method 36 Table 4.2 Values of f sfor maximum sample standard deviation (MSSD) for combined control of double specification limits Tightened inspection, “s” method 37 Table 4.3 Values of f sfor maximum sample standard deviation (MSSD) for combined control o
22、f double specification limits Reduced inspection, “s” method 38BS 6002-3:2005 BSI 31 March 2005 iii Page Table 5.1 Values of f for maximum process standard deviation (MPSD) for combined control of double specification limits “ ” method 38 Table 5.2 Values of f for maximum process standard deviation
23、(MPSD) for separate control of double specification limits “ ” method 39 Table 5.3 Values of f for maximum process standard deviation (MPSD) for complex control of double specification limits “ ”m et h o d 4 0 Table 6 Estimated process average, as a function of the quality statistic Q for sample siz
24、e 3 “s” method 41 Table 7.1 Form p* double sampling plans for normal inspection (master table) “s” method) 43 Table 7.2 Form p* double sampling plans for tightened inspection (master table) “s” method 44 Table 7.3 Form p* double sampling plans for reduced inspection (master table) “s” method 45 Tabl
25、e 8.1 Form p* double sampling plans for normal inspection (master table) “ ” method 46 Table 8.2 Form p* double sampling plans for tightened inspection (master table) “ ” method 47 Table 8.3 Form p* double sampling plans for reduced inspection (master table) “ ” method 48 Table 9 Values of c Ufor up
26、per control limit of sample standard deviation 49 Table E.1 Values of a n 73 Table F.1 Matched single sampling plans of Form k for normal inspection “s” method 76 Table F.2 Matched single sampling plans of Form k for tightened inspection “s” method 77 Table F.3 Matched single sampling plans of Form
27、k for reduced inspection “s” method 78 Table G.1 Matched single sampling plans of Form k for normal inspection “ ” method 79 Table G.2 Matched single sampling plans of Form k for tightened inspection “ ” method 80 Table G.3 Matched single sampling plans of Form k for reduced inspection “ ” method 81
28、 Table H.1 Average sample numbers for double sampling under normal inspection “s”me th od 82 Table H.2 Average sample numbers for double sampling under tightened inspection “s”m et h od 8 3 Table H.3 Average sample numbers for double sampling under reduced inspection “s”met hod 84 Table I.1 Producer
29、s risks under normal inspection (in percent) “s” method 85 Table I.2 Producers risks under tightened inspection (in percent) “s” method 86 Table I.3 Producers risks under reduced inspection (in percent) “s” method 87 Table J.1 Tabulated “ ” method OCs for code letter C (normal and tightened inspecti
30、on) and E (reduced inspection) 88 Table J.2 Tabulated “ ” method OCs for code letter D (normal and tightened inspection) and F (reduced inspection) 88 Table J.3 Tabulated “ ” method OCs for code letter E (normal and tightened inspection) and G (reduced inspection) 89 Table J.4 Tabulated “ ” method O
31、Cs for code letter F (normal and tightened inspection) and H (reduced inspection) 89 p BS 6002-3:2005 iv BSI 31 March 2005Page Table J.5 Tabulated “ ” method OCs for code letter G (normal and tightened inspection) and J (reduced inspection) 90 Table J.6 Tabulated “ ” method OCs for code letter H (no
32、rmal and tightened inspection) and K (reduced inspection) 90 Table J.7 Tabulated “ ” method OCs for code letter J (normal and tightened inspection) and L (reduced inspection) 91 Table J.8 Tabulated “ ” method OCs for code letter K (normal and tightened inspection) and M (reduced inspection) 91 Table
33、 J.9 Tabulated “ ” method OCs for code letter L (normal and tightened inspection) and N (reduced inspection) 92 Table J.10 Tabulated “ ” method OCs for code letter M (normal and tightened inspection) and P (reduced inspection) 92 Table J.11 Tabulated “ ” method OCs for code letter N (normal and tigh
34、tened inspection) and Q (reduced inspection) 93 Table J.12 Tabulated “ ” method OCs for code letter P (normal and tightened inspection) and R (reduced inspection) 93 Table J.13 Tabulated “ ” method OCs for code letter Q (normal and tightened inspection) 94 Table J.14 Tabulated “ ” method OCs for cod
35、e letter R (normal and tightened inspection) 94 Table K.1 Minimum and maximum values of the ratios of the ASNs “s” method 95 Table K.2 Minimum and maximum values of the ratios of the ASNs “ ” method 96 Table L.1 Minimum and maximum ASN ratios for normal inspection 97 Table L.2 Minimum and maximum AS
36、N ratios for tightened inspection 98 Table L.3 Minimum and maximum ASN ratios for reduced inspection 99BS 6002-3:2005 BSI 31 March 2005 v Foreword This British Standard was prepared by Technical Committee SS/5. BS 6002 is being developed into a multi-part standard. The standard will be issued in thr
37、ee parts: Part 1: Specification for single sampling plans indexed by acceptance quality limit (AQL) for lot-by-lot inspection Single quality characteristic and single AQL; Part 2: General specification for single sampling plans indexed by acceptance quality limit (AQL) for lot-by-lot inspection; Par
38、t 3: Guide to double sampling plans indexed by acceptance quality limit (AQL) for lot-by-lot inspection. In all three parts of BS 6002: a) the acronym AQL now stands for “acceptance quality limit” rather than “acceptable quality level”, in order to more accurately reflect its function; b) procedures
39、 are given for the case where the process standard is unknown (the “s” method) and for the case where it may be presumed to be known (the “ ”m et h o d); c) the sampling plans have been chosen so that their operating characteristic curves closely match those of the corresponding single sampling plan
40、s in BS 6001-1; d) minimal statistical theory has been given (it being planned ultimately to provide this in a guidance document to sampling procedures for inspection by variables); e) text, charts and tables that are only informative have been consigned to annexes wherever practicable. In none of t
41、he three parts have methods been given based on the sample range, now that the availability of computers and calculators with a standard deviation function key is so widespread. Data for acceptance sampling by variables is often substantially more expensive to acquire than data for sampling by attri
42、butes, and the “s” method makes more efficient use of these data. The coverage of BS 6002-1 is constrained to the case of a single, normally distributed, quality characteristic with a single class of nonconformity, and includes the case of combined control of double specification limits. BS 6002-2 p
43、rovides a more comprehensive treatment of single sampling plans by variables, including procedures for separate and complex control of double specification limits. Procedures are also given for multiple independent quality characteristics and/or multiple AQLs.BS 6002-3:2005 vi BSI 31 March 2005 BS 6
44、002-3 provides plans for double sampling by variables, which on average provide substantial savings of inspection effort in comparison with single sampling plans by variables. The savings are achieved by first selecting from the lot and inspecting a random sample that is typically nearly 40 % smalle
45、r than that of the corresponding single sampling plan. If these inspection results satisfy an acceptance criterion, an immediate decision is made to accept the lot without further inspection. Alternatively, if the inspection results satisfy a non-acceptance criterion, an immediate decision not to ac
46、cept the lot is made without further inspection. Thus, when quality is very good or very poor, the saving in inspection effort can amount to nearly 40 %. Only when the inspection results from the first sample are equivocal is a second random sample, of the same size as the first, selected; the accep
47、tability of the lot is then resolved by combining the results of the first and second samples and determining whether they satisfy a second acceptance criterion. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application
48、. Compliance with a British Standard does not of itself confer immunity from legal obligations Summary of pages This document comprises a front cover, an inside front cover, pages i to vi, pages 1 to 101 and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued.BS 6002-3:2005 BSI 31 March 2005 1 Introduction Inspection by variables for percent nonconforming items, as described in the present document, includes several possible modes, the combination of which leads to a p
