ISO 25337-2010 Plastics - Production quality control - Statistical method for using single measurements《塑料 产品质量控制 单一测量用统计方法》.pdf

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1、 Reference number ISO 25337:2010(E) ISO 2010INTERNATIONAL STANDARD ISO 25337 First edition 2010-03-15 Plastics Production quality control Statistical method for using single measurements Plastiques Contrle de qualit en production Mthode statistique pour lutilisation de mesurages uniques ISO 25337:20

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6、elow or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2010 All rights reservedISO 25337:2010(E) ISO 2010 All rights reserved

7、 iiiContents Page Foreword iv Introduction.v 1 Scope1 2 Normative references1 3 Terms and definitions .1 4 Precision of test methods.2 5 Single measurements for production quality control purposes 3 5.1 General .3 5.2 Variability of the production process and test method.3 5.3 Within-laboratory repr

8、oducibility.4 5.4 Calculation of s RLabfrom a within-laboratory reproducibility investigation4 5.5 Interpretation of single-measurement data for production quality control purposes .5 6 Procedure.8 Annex A (informative) Example of the calculation of s Rlabfrom a within-laboratory reproducibility inv

9、estigation 9 Annex B (informative) Examples of the effect on production limits of making duplicate and triplicate measurements as opposed to single measurements11 Annex C (normative) Reducing the probability of incorrectly accepting a nonconforming product 15 Bibliography17 ISO 25337:2010(E) iv ISO

10、2010 All rights reservedForeword 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

11、 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 Commiss

12、ion (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical

13、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 document may be the subject of patent rights. ISO shall

14、not be held responsible for identifying any or all such patent rights. ISO 25337 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 5, Physical-chemical properties. ISO 25337:2010(E) ISO 2010 All rights reserved vIntroduction Many ISO standard test methods specify that measurem

15、ents be made in duplicate or even in more than duplicate. In some cases, repeated operations are also specified. However, for production quality control it is common practice to carry out single measurements. For many production environments, replicates and/or repeated operations, as specified in ma

16、ny ISO standards, are time-consuming and expensive and could result in an undesirable increase in production costs. Furthermore, the laboratory response time could also increase unacceptably. This International Standard presents a statistical method for using only single measurements in a production

17、 environment, in accordance with ISO test method standards which specify at least duplicate measurements and/or repeated operations. This International Standard is likely to be of interest to companies using ISO test methods in production quality control and recorded in their quality management syst

18、em. This International Standard is not intended to be used for publishing data, for marketing purposes or for the development of customer specifications/designations. Provided the statistical computations support the reduction in the number of replicates for a particular test, reduction from duplica

19、te replicates to a single measurement is possible, as is reduction in the number of replicates for a test result to half, or even less than half, the specified number of replicates. A reduction in the variability of a test method might be necessary before a reduction in the number of test replicates

20、 can be considered 1) . Technical Committee ISO/TC 61, Plastics, considers that such a model might not only be of importance in the field of plastics but also of interest in other fields in which ISO test methods are used in production quality control. Single measurements are often used for quality

21、control tests. The “single-measurement model” presented in this International Standard forms a basis for carrying out single measurements for production quality control; reducing the number of replicate tests carried out and/or modifying test methods using multiple test samples in order to reduce la

22、boratory costs and decrease the laboratory response time; modifying test methods which specify repeated operations (as is usually the case with, e.g., drying to constant mass) to give a test method which involves only one operation, leading to shorter response times and lower laboratory costs; handl

23、ing results that lie outside the production and/or acceptance limits; achieving cost savings by harmonizing material production limits with the test methods used, taking into account the precision of the test method and the production capacity. Furthermore, when specified by the responsible authorit

24、y, the single-measurement model described in this International Standard can be used as a reference in, for example, product specifications, in sales agreements and in communicating with customers. 1) An Excel-based tool for the calculation of repeatability and reproducibility parameters has been de

25、veloped by ISO/TC 61/SC 5 and is expected to become available on the ISO web site for on-line calculations at some future point in time, initially at a password-protected location reserved for those participating in the development of ISO standards. The calculation model is based on that of ISO 5725

26、 and is applicable to balanced and unbalanced data sets. INTERNATIONAL STANDARD ISO 25337:2010(E) ISO 2010 All rights reserved 1Plastics Production quality control Statistical method for using single measurements 1 Scope This International Standard describes a statistical, so-called single-measureme

27、nt, model (SD model) for using single measurements for production quality control purposes at a producers manufacturing site, even if a standard test method specifies replicate measurements. The statistical model is also applicable to test methods which call for repeated operations. A general approa

28、ch to the precision statement in test method standards which produce numerical results is also described. The statistical model is only applicable to test methods which give results that follow a normal (i.e. Gaussian) distribution. The principle of the statistical model is based on the determinatio

29、n of upper and lower production limits, taking into account the accuracy and the reproducibility of the test method, the latter being added to the production limits in order to define an area outside the production limits in which a test result can fall owing to the nature of the production process

30、and/or the test method. This International Standard is designed for project managers, heads of laboratories and production managers. However, the support of a statistician is highly recommended, and sometimes indispensable, for providing the necessary technical backup and statistical analysis. If th

31、is International Standard is used in combination with a test method standard, this needs to be clearly indicated in all relevant documents, e.g. product specifications, production process specifications and contracts. 2 Normative references The following referenced documents are indispensable for th

32、e application 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 5725-1, Accuracy (trueness and precision) of measurement methods and results Part 1: General principles

33、and definitions 3 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 5725-1 and the following apply. 3.1 production process standard deviation s Pstandard deviation for the production process 3.2 production and test method standard deviation s P communica

34、tion between the interested parties; comparison with (internal) laboratory performance; use as a basis for inter-laboratory comparisons; harmonization of test methods between interested parties; statistical process control. ISO 25337:2010(E) ISO 2010 All rights reserved 3A practical guide, specially

35、 designed for project leaders and heads of laboratories, to the determination of the precision of a test method is given in Reference 9 (see the Bibliography). However, it should be noted that the support of a statistician is recommended, and sometimes indispensable, for providing the technical back

36、up necessary for the RRI programme and the statistical analysis of the data obtained. 5 Single measurements for production quality control purposes 5.1 General Many ISO standards specify that measurements be made twice or even more. In many test method standards, repeated operations are also specifi

37、ed. The reported test result is the average, or another appropriate function such as the median, of the individual observations. The object of the procedures of this International Standard is to use single measurements for production quality control purposes within a producers manufacturing site in

38、a considered statistical manner, even if a standard test method specifies replicate measurements. For production quality control, it is common practice to carry out single measurements since, in many production situations, replicate measurements are too time-consuming and expensive and the laborator

39、y response time could also increase unacceptably. For production quality control purposes, single measurements based on and with reference to this International Standard and statistically validated are permitted when specified by the responsible authority, even if the test method standard specifies

40、replicate measurements. For test methods where a set of specimens ( 2) is considered as giving a single test result, the model can in some cases also be used to reduce the number of specimens in a set. However, it should be noted that, for test methods where a set of specimens is considered as givin

41、g a single test result, the number of test specimens is, in most cases, the minimum necessary to obtain a reliable test result, due to the spread in results caused by inhomogeneity in the sample, preparing the test specimens, etc. Reduction in the variability of a test method might be necessary befo

42、re a reduction in the number of test replicates can be considered. Therefore, any reduction in the number of test specimens in a set that is considered as giving a single test result shall only be carried out in close cooperation with a statistician. For test methods which specify repeated procedure

43、s or operations carried out on a sample, such as drying to constant mass, the SD method can also be used to reduce the number of operations to possibly only one operation. A statistician should preferably be consulted for the necessary statistical guidance. The effect on production limits of making

44、duplicate and triplicate measurements as opposed to single measurements is shown by two examples given in Clauses B.2 and B.3 in Annex B. 5.2 Variability of the production process and test method The variability of measurements made on items from a production process consists of the variability of t

45、he production process itself and the variability of the test method used to check the production process. The lower and upper production limits, L PLand U PL , which include the variability of the test method, are calculated for a stable production period. For a non-standard normal distribution prod

46、uction process, the lower and upper production limits shall be calculated by a statistician. For a standard normal distribution production process, the standard deviation, s P&T(the production and test method standard deviation), can be calculated for a stable production period. s P&Tcan also be det

47、ermined from production data over, for example, a period of one year. However, data from production runs in which irregularities or outliers are known to have occurred shall not be used. For a two-sided precision interval of 99,73 %, the production data will be within the range 3s P&T(k-factor = 3) relative to the average value. For