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1、BRITISH STANDARD BS 7037-1: 1988 ISO 5538:1987 Sampling plans for milk and milk products Part 1: Specification for inspection by attributes UDC 637.11.3:620.113 Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:50:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI B
2、S 7037-1:1988 This British Standard, having been prepared under the direction of the Dairying Standards Committee, was published under the authority of the Board of BSI and comes into effect on 30 November 1988 BSI 11-1999 The following BSI references relate to the work on this standard: Committee r
3、eference DAC/5 Draft for comment 86/52583 DC ISBN 0 580 16924 3 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Dairying Standards Committee (DAC/-) to Technical Committee DAC/5, upon which the following bodies were represented: AFRC Ins
4、titute of Food Research (Reading Laboratory) Association of Clinical Pathologists Department of Health and Social Security Ice Cream Alliance Limited Institute of Trading Standards Administration Institution of Environmental Health Officers Intervention Board for Agricultural Produce Milk Marketing
5、Board Milk Marketing Board for Northern Ireland Ministry of Agriculture, Fisheries and Food Royal Association of British Dairy Farmers Society of Chemical Industry Society of Dairy Technology Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: London South Bank Universit
6、y, London South Bank University, Fri Dec 08 13:50:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7037-1:1988 BSI 11-1999i Contents Page Committees responsibleInside front cover National forewordii 0Introduction1 1Scope and field of application1 2References1 3Definitions1 4ISO 2859 sampling plans1
7、5Selection of sampling plan1 6Records2 7Selection of units2 Annex A Statistical theory9 Annex B Critical defects9 Annex C Drawing of samples10 Table 1.1 Inspection Level I AQL = 2,5 %3 Table 1.2 Inspection Level I AQL = 4,0 %3 Table 1.3 Inspection Level I AQL = 6,5 %3 Table 1.4 Inspection Level I AQ
8、L = 10 %3 Table 2.1 Inspection Level S-4 AQL = 2,5 %4 Table 2.2 Inspection Level S-4 AQL = 4,0 %4 Table 2.3 Inspection Level S-4 AQL = 6,5 %4 Table 2.4 Inspection Level S-4 AQL = 10 %4 Table 3.1 Inspection Level S-3 AQL = 2,5 %5 Table 3.2 Inspection Level S-3 AQL = 4,0 %5 Table 3.3 Inspection Level
9、S-3 AQL = 6,5 %5 Table 3.4 Inspection Level S-3 AQL = 10 %5 Table 4.1 Inspection Level S-2 AQL = 2,5 %5 Table 4.2 Inspection Level S-2 AQL = 4,0 %5 Table 4.3 Inspection Level S-2 AQL = 6,5 %6 Table 4.4 Inspection Level S-2 AQL = 10 %6 Table 5.1 Inspection Level S-1 AQL = 2,5 %6 Table 5.2 Inspection
10、Level S-1 AQL = 4,0 %6 Table 5.3 Inspection Level S-1 AQL = 6,5 %6 Table 5.4 Inspection Level S-1 AQL = 10 %6 Table 6 Single sampling plans at AQL = 2,5 %7 Table 7 Single sampling plans at AQL = 4,0 %7 Table 8 Single sampling plans at AQL = 6,5 %7 Table 9 Single sampling plans at AQL = 10 %8 Table 1
11、0 Random sampling numbers13 Publications referred toInside back cover Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:50:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7037-1:1988 ii BSI 11-1999 National foreword This Part of BS 7037 has been prepared under
12、 the direction of the Dairying Standards Committee. It is identical with ISO 5538:1987 “Milk and milk products Sampling Inspection by attributes”, published by the International Organization for Standardization (ISO). The sampling plans specified in the International Standard have been developed joi
13、ntly with the International Dairy Federation and the Association of Official Analytical Chemists, and will also be published by those organizations. Terminology and conventions. The text of the International Standard has been approved as suitable for publication as a British Standard without deviati
14、on. Some terminology and certain conventions are not identical with those used in British Standards; attention is drawn especially to the following. The comma has been used as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. Whe
15、re the words “International Standard” appear, referring to this standard, they should be read as “Part of BS 7037”. Additional information. It is intended that BS 7037-2 will implement, when available, ISO 8197 “Milk and milk products Sampling Inspection by variables” which is in preparation. A Brit
16、ish Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-references International StandardCorrespo
17、nding British Standard ISO 707:1985BS 809:1985 Methods for sampling of milk and milk products (Identical) ISO 2859:1974BS 6001 Sampling procedures for inspection by attributes Part 1:1972 Specification for sampling plans indexed by acceptable quality level (AQL) for lot-by-lot inspection (Technicall
18、y equivalent) ISO 2859:1974/ Addendum No. 1:1977 BS 6000:1972 Guide to the use of BS 6001, sampling procedures and tables for inspection by attributes (Technically equivalent) ISO 3534:1977BS 5532 Statistical terminology Part 1:1978 Glossary of terms relating to probability and general terms relatin
19、g to statistics (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 16, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the
20、 amendment table on the inside front cover. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:50:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7037-1:1988 BSI 11-19991 0 Introduction The sampling theory used in this International Standard is based on classif
21、ying a unit as “good” or “defective”. A “good” unit is one which meets the requirements of a specification, while a “defective” unit is one which does not. It is essential that the sample is taken at random. If it is not, the sampling plans will not give the stated protection. See Annex A. 1 Scope a
22、nd field of application 1.1 This International Standard specifies sampling plans for the inspection by attributes of milk and milk products. It is intended to be used to choose a sample size for any situation where it is required to measure the conformity to a specification of a lot of a dairy produ
23、ct by examination of a representative sample. Methods of sampling for milk and milk products are given in ISO 707. 1.2 This International Standard is applicable to the sampling of all milk products submitted in discrete lots, irrespective of whether the lots are from the same production. The accepta
24、nce or otherwise of any lot is a matter for the parties to a contract and is outside the scope of this International Standard. 1.3 This International Standard is intended to be used in all cases where attribute sampling plans are required for a dairy product, except that if specific compositional st
25、andards, specifications or contracts include different sampling schemes, those schemes are to be used. 1.4 This International Standard is not applicable to sampling for microbiological defects, unless otherwise agreed by the interested parties. 2 References ISO 707, Milk and milk products Methods of
26、 sampling. ISO 2859:1974, Sampling procedures and tables for inspection by attributes1). ISO 2859:1974/Addendum 1:1977, General information on sampling inspection, and guide to the use of the ISO 2859 tables1). ISO 3534, Statistics Vocabulary and symbols. 3 Definitions For the purpose of this Intern
27、ational Standard, the definitions given in ISO 3534 apply. 4 ISO 2859 sampling plans ISO 2859 describes plans for use in all situations, and gives an account of the theoretical background to the sampling tables. The plans are indexed by batch or lot size and acceptable quality level (AQL). AQL is de
28、fined in ISO 2859 and in its Addendum 1; it can be considered to be the average level of quality which if maintained by a producer would result in the acceptance of most of his production. 5 Selection of sampling plan 5.1 Classification of defects Before selection of a sampling plan, the contract or
29、 specification shall clearly define all critical, major and minor defects in such a way that they are unambiguously understood by all users of the contract, specification or document containing or referring to the sampling plan. 5.1.1 A critical defect is one that would make the product unacceptable
30、. For the purpose of this International Standard, critical defects relate to the presence of toxic contaminants at a critically high level. Examples include heavy metals and pesticide residues. In this case, the method to be adopted shall be that described in Annex B2). It is necessary to decide on
31、an acceptable risk of not detecting a certain percentage of defectives, where a defective is a unit which contains more than the critical level of the contaminant. It is impossible to guarantee freedom from contamination. 5.1.2 A major defect is one that is likely to make the product unfit for use,
32、i.e., in the case of milk and milk products, unfit for sale to the consumer. A major defect would result in the product spoiling or becoming unfit for sale or processing. Examples include a) composition defect, where this would affect keeping quality; b) contamination with inhibitory substances; c)
33、integrity of packaging; d) visible contamination with dirt. Sampling plans for major defects shall be selected from the tables using an AQL of not more than 6,5 %. 1) The edition of ISO 2859 relevant to this International Standard is currently under revision. Any necessary alterations, for example i
34、n terminology, as a consequence of this revision will be carried out to this International Standard when it is next revised. 2) Annex B is an extract of clause 9 of ISO 2859/Addendum 1. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:50:03 GMT+00:00 2006, Unc
35、ontrolled Copy, (c) BSI BS 7037-1:1988 2 BSI 11-1999 5.1.3 A minor defect is a failure to comply with a specification, but which does not make the unit unfit for use and sale, nor cause it to spoil. Examples include a) a unit, the chemical composition or net content of which falls outside, but close
36、 to, a specification limit; b) small abnormalities in appearance. Sampling plans for minor defects shall be selected from the tables using an AQL of not more than 10 %. 5.2 Choice of inspection level and AQL 5.2.1 The sampling plan shall be selected from the tables, using the lot size and the agreed
37、 AQL. In these tables, n is the sample size, Ac is the acceptance number, and Re is the rejection number. Example: For a sample size of n = 13, Ac = 0 and Re = 1, this means that if a sample of 13 units contains no defectives, the lot shall be accepted; if the sample contains 1 defective, the lot sh
38、all be rejected. Table 1 to Table 5 are derived from ISO 2859 and refer to Inspection Levels I, S-4, S-3, S-2 and S-1. Inspection Level I is preferred. Using any of the S plans will result in increased risks, and they shall not be used without first checking that the associated risk is acceptable. D
39、etails of these risks are given in 5.2.2. 5.2.2 Inspection Levels S-4, S-3, S-2 and S-1 may be used where relatively small sample sizes are necessary and large sample risks can or must be tolerated. As a consequence of using these special levels, there is an increased probability of making a wrong d
40、ecision. Firstly, the consumers risk increases. This is illustrated in Table 6 to Table 9. Table 6 refers to plans with an AQL of 2,5 %, Table 7 to an AQL of 4,0 %, Table 8 to an AQL of 6,5 % and Table 9 to an AQL of 10 %. Each table contains: the sample size (n) and the appropriate lot size at the
41、separate inspection levels; maximum number of defective units permitted in the sample acceptance number (Ac); minimum number of defective units required in the sample to reject the lot rejection number (Re); limiting quality LQ. If the sample size is small, LQ is high; if the sample size increases,
42、LQ is reduced at the same AQL. For example, in Table 6, the inspection plan in which the sample size is 5 and LQ = 45 % appears in all the inspection levels but only at S-1 level can all lot sizes be inspected. At the S-4 and I Inspection Levels the sample size of 5 can only be taken when the lot si
43、ze does not exceed 150. The fact that the consumers risk (and at the same time the LQ) becomes smaller as the size of the inspected lot becomes greater, is justified on economic grounds. Inspection plans in which the LQ is several times greater than the AQL are unsuitable for both consumer and produ
44、cer. If a lot of 35 000 units is considered, Inspection Level I would require a sample size of 125, giving an LQ of 11 % (i.e. 95 % of lots containing 11 % of defects would be rejected). S-1 would require a sample size of 5, giving an LQ of 45 %. An LQ of 45 % is so much greater than the AQL of 2,5
45、% that the concept of AQL has become meaningless. Furthermore, the sample of 5 would wrongly reject more than 10 % of lots containing 2,5 % of defects. Increasing the sample size increases both the protection to the consumer, and the discrimination of the sampling plan; this increased discrimination
46、 is one of the major reasons for relating sample size to lot size. Users of this International Standard will find full operating characteristics for each plan in ISO 2859; these relate the probability of acceptance to per cent defective in the lot. 6 Records Successful operation of this type of samp
47、ling plan requires the maintenance of comprehensive records of the results of inspection, and the plan in use. Interchange of information between both parties would be useful, and it is recommended that each party make such information available to the other as required. 7 Selection of units The sam
48、pling theory used for the plans in ISO 2859 and thus in this International Standard assumes that sampling is at random, which means that each unit in the lot should have the same probability of appearing in the sample. Every effort shall be made to obtain a random sample. Whenever possible a formal
49、randomization procedure, as described in ISO 2859/Addendum 1, clause 15, should be used (see Annex C). If this is not done, the risks associated with the plans cannot be assumed to be those expected. Formal randomization is not difficult, although it can be tedious and time-consuming. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:50:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7037-1:1988 BSI 11-19993 Table 1.1 Insp