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1、BRITISH STANDARD BS ISO 5725-6:1994 Incorporating Technical Corrigendum No. 1 Implementation of ISO 5725-6:1994 Accuracy (trueness and precision) of measurement methods and results Part 6: Use in practice of accuracy values NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Licen
2、sed Copy: sheffieldun sheffieldun, na, Sun Nov 26 04:27:29 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 5725-6:1994 This British Standard, having been prepared under the direction of the Management Systems Sector Board (S/-), was published under the authority of the Standards Board and comes in
3、to effect on 15 April 1995 BSI 09 May 2002 The following BSI references relate to the work on this standard: Committee reference QMS/16 Draft for comment 90/97781 DC ISBN 0 580 24024 X Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technica
4、l Committee QMS/16, Precision of test methods, upon which the following bodies were represented: British Gas plc Chemical Industries Association Consumers Association Department of Trade and Industry (Laboratory of the Government Chemist) Department of Trade and Industry (National Physical Laborator
5、y) Institute of Quality Assurance Ministry of Agriculture, Fisheries and Food Ministry of Defence Royal Society of Chemistry University of London Amendments issued since publication Amd. No.DateComments 13574 Technical Corrigendum No. 1 09 May 2002 Revision of Table 14 and 8.4.9.2.2a) Licensed Copy:
6、 sheffieldun sheffieldun, na, Sun Nov 26 04:27:29 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 5725-6:1994 BSI 09 May 2002 i Contents Page Committees responsibleInside front cover National forewordii Forewordiv Text of ISO 5725-61 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 04:27:29
7、GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 5725-6:1994 ii BSI 09 May 2002 National foreword This British Standard reproduces verbatim ISO 5725-6:1994, including Technical Corrigendum October 2001, and implements it as the UK national standard. Parts 1 to 6 of BS ISO 5725 together supersede BS
8、 5497-1:1987, which is withdrawn. This British Standard is published under the direction of the Information Systems Technology Standards Policy Committee whose Technical Committee QMS/16 has the responsibility to: aid enquirers to understand the text; present to the responsible international committ
9、ee any enquiries on interpretation, or proposals for change, and keep UK interests informed; monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this committee can be obtained on request to its secretary. NOTEInternational and
10、 European Standards, as well as overseas standards, are available from Customer Services, BSI, 389 Chiswick High Road, London W4 4AL. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue
11、 under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their corre
12、ct application. 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 and ii, the ISO title page, pages ii to iv, pages 1 to 49 and a back cover. The BSI copyright notice di
13、splayed in this document indicates when the document was last issued. Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 04:27:29 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 04:27:29 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 5725-6:1994
14、ii BSI 09 May 2002 Contents Page Forewordiv Introduction1 1Scope1 2Normative references2 3Definitions2 4Determination of limits2 4.1Repeatability and reproducibility limits2 4.2Comparisons based on more than two values3 5Methods for checking the acceptability of test results and determining the fina
15、l quoted result5 5.1General5 5.2Methods for checking the acceptability of test results obtained under repeatability conditions5 5.3Methods for checking the acceptability of test results obtained under both repeatability and reproducibility conditions12 6Method for checking the stability of test resu
16、lts within a laboratory14 6.1Background14 6.2Methods for checking stability15 7Use of repeatability and reproducibility standard deviations in assessing laboratories30 7.1Assessment method30 7.2Evaluation of the use of a measurement method by a laboratory not previously assessed30 7.3Continued asses
17、sment of previously approved laboratories34 8Comparison of alternative measurement methods39 8.1Origin of alternative measurement methods39 8.2Purpose of comparing measurement methods39 8.3Method B is a candidate for an alternative standard method (“Standardization experiment” not defined)39 8.4Accu
18、racy experiment40 8.5Method B is a candidate for a routine method46 Annex A (normative) Symbols and abbreviations used in ISO 572548 Figure 1 Method for checking the acceptability of test results, obtained under repeatability conditions, when two test results are obtained to start with and obtaining
19、 test results is inexpensive: Case 5.2.2.17 Figure 2 Method for checking the acceptability of test results, obtained under repeatability conditions, when two test results are obtained to start with and obtaining test results is expensive: Case 5.2.2.2a)8 Figure 3 Method for checking the acceptabilit
20、y of test results, obtained under repeatability conditions, when two test results are obtained to start with and obtaining test results is expensive: Case 5.2.2.2b)9 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 04:27:29 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 5725-6:1994 BSI 09 May
21、2002 iii Page Figure 4 Method for checking the acceptability of test results, obtained under repeatability conditions, when n test results are obtained to start with and obtaining test results is inexpensive: Case A10 Figure 5 Method for checking the acceptability of test results, obtained under rep
22、eatability conditions, when n test results are obtained to start with and obtaining test results is expensive: Case B10 Figure 6 Method for checking the acceptability of test results, obtained under repeatability conditions, when n ? 5 and obtaining test results is inexpensive, or n ? 4 and obtainin
23、g test results is expensive: Case C11 Figure 7 Range chart for the nickel content (%) of a private reference material, obtained under repeatability conditions19 Figure 8 Range chart for the sulfur content (%) in blast-furnace coke, obtained under time-and-operator-different intermediate precision co
24、nditions21 Figure 9 Shewhart control chart for of the ash content % (m/m) of a private reference material25 Figure 10 Cumulative sum control chart for of the ash content % (m/m) of a private reference material26 Figure 11 Shewhart control chart for of the As content for the silver diethyldithiocarba
25、mate-arsine evolution colorimetric procedure for arsenic in zinc oxide27 Figure 12 Cumulative sum control chart for of the As content for the silver diethyldithiocarbamate-arsine evolution colorimetric procedure for arsenic in zinc oxide27 Table 1 Critical range factors, f(n)6 Table 2 Values of c(n)
26、14 Table 3 Classification for characteristics of test materials according to their true values and important parameters for checking accuracy (trueness and precision) of results16 Table 4 Factors for computing a range chart17 Table 5 Control chart data sheet for example 1 (6.2.2)18 Table 6 Control c
27、hart data sheet for example 2 (6.2.3)22 Table 7 Control chart data sheet for example 3 (6.2.4)24 Table 8 -chart data sheet for example 4 (6.2.5)29 Table 9 Cement content of concrete32 Table 10 Cell means and ranges32 Table 11 Alkalinity of water36 Table 12 Cell means of Table 1136 Table 13 Cell rang
28、es of Table 1137 Table 14 Values of ?(vA, vB, ?, ?) or ?(vA, vB, ?, ?) for ? = 0,05 and ? = 0,0542 ? ? x x x Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 04:27:29 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 5725-6:1994 iv BSI 09 May 2002 Foreword ISO (the International Organization for
29、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 for which a technical committee has been established has the r
30、ight 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) on all matters of electrotechnical standardization. Draft Inter
31、national Standards 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. International Standard ISO 5725-6 was prepared by Technical Committee ISO/TC 69, App
32、lications of statistical methods, Subcommittee SC 6, Measurement methods and results. ISO 5725 consists of the following parts, under the general title Accuracy (trueness and precision) of measurement methods and results: Part 1: General principles and definitions; Part 2: Basic method for the deter
33、mination of repeatability and reproducibility of a standard measurement method; Part 3: Intermediate measures of the precision of a standard measurement method; Part 4: Basic methods for the determination of the trueness of a standard measurement method; Part 5: Alternative methods for the determina
34、tion of the precision of a standard measurement method; Part 6: Use in practice of accuracy values. Parts 1 to 6 of ISO 5725 together cancel and replace ISO 5725:1986, which has been extended to cover trueness (in addition to precision) and intermediate precision conditions (in addition to repeatabi
35、lity and reproducibility conditions). Annex A forms an integral part of this part of ISO 5725. Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 04:27:29 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 5725-6:1994 BSI 09 May 2002 1 Introduction 0.1 ISO 5725 uses two terms “trueness” and “precisi
36、on” to describe the accuracy of a measurement method. “Trueness” refers to the closeness of agreement between the arithmetic mean of a large number of test results and the true or accepted reference value. “Precision” refers to the closeness of agreement between test results. 0.2 The need to conside
37、r “precision” arises because tests performed on presumably identical materials in presumably identical circumstances do not, in general, yield identical results. This is attributed to unavoidable random errors inherent in every measurement procedure; the factors that influence the outcome of a measu
38、rement cannot all be completely controlled. In the practical interpretation of measurement data, this variability has to be taken into account. For instance, the difference between a test result and some specified value may be within the scope of unavoidable random errors, in which case a real devia
39、tion from such a specified value has not been established. Similarly, comparing test results from two batches of material will not indicate a fundamental quality difference if the difference between them can be attributed to the inherent variation in the measurement procedure. 0.3 Parts 1 to 5 of IS
40、O 5725 discuss the background to, and given methods for, the assessment of the precision (in terms of the repeatability standard deviation and the reproducibility standard deviation) and the trueness (in terms of the various components of bias) of measurements produced by a standard measurement meth
41、od. Such assessment would, however, be pointless if there were no practical uses to which the results could be put. 0.4 Given that the accuracy of a measurement method has been established, this part of ISO 5725 applies that knowledge in practical situations in such a way as to facilitate commercial
42、 transactions and to monitor and improve the operational performance of laboratories 1 Scope 1.1 The purpose of this part of ISO 5725 is to give some indications of the way in which accuracy data can be used in various practical situations by: a) giving a standard method of calculating the repeatabi
43、lity limit, the reproducibility limit and other limits to be used in examining the test results obtained by a standard measurement method; b) providing a way of checking the acceptability of test results obtained under repeatability or reproducibility conditions; c) describing how to assess the stab
44、ility of results within a laboratory over a period of time, and thus providing a method of “quality control” of the operations within that laboratory; d) describing how to assess whether a given laboratory is able to use a given standard measurement method in a satisfactory way; e) describing how to
45、 compare alternative measurement methods. 1.2 This part of ISO 5725 is concerned exclusively with measurement methods which yield measurements on a continuous scale and give a single numerical figure as the result, although this single figure may be the outcome of a calculation from a set of observa
46、tions. 1.3 It is assumed that the estimates of trueness and precision for the method have been obtained in accordance with parts 1 to 5 of ISO 5725. 1.4 Any additional information regarding the field of application will be given at the beginning of each particular application. Licensed Copy: sheffie
47、ldun sheffieldun, na, Sun Nov 26 04:27:29 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 5725-6:1994 2 BSI 09 May 2002 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this part of ISO 5725. At the time of publication,
48、the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this part of ISO 5725 are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of current
49、ly valid International Standards. ISO 3534-1:1993, Statistics Vocabulary and symbols Part 1: Probability and general statistical terms. ISO 5725-1:1994, Accuracy (trueness and precision) of measurement methods and results Part 1: General principles and definitions. ISO 5725-2:1994, Accuracy (trueness and precision) of measurement methods and results Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method. ISO 5725-3:1994, Accuracy (tru