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 LAWBS ISO
2、 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 into effect on 15 April 1995 BSI 09 May 2002 The following BSI references relate to the work on this standard:
3、 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 Technical Committee QMS/16, Precision of test methods, upon which the following bodies were represented: British Gas
4、 plc Chemical Industries Association Consumers Association Department of Trade and Industry (Laboratory of the Government Chemist) Department of Trade and Industry (National Physical Laboratory) Institute of Quality Assurance Ministry of Agriculture, Fisheries and Food Ministry of Defence Royal Soci
5、ety of Chemistry University of London Amendments issued since publication Amd. No. Date Comments 13574 Technical Corrigendum No. 1 09 May 2002 Revision of Table 14 and 8.4.9.2.2a)BS ISO 5725-6:1994 BSI 09 May 2002 i Contents Page Committees responsible Inside front cover National foreword ii Forewor
6、d iv Text of ISO 5725-6 1BS 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 5497-1:1987, whic
7、h is withdrawn.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 committee any enquiries o
8、n 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. NOTE International and European Standar
9、ds, 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 under the sectio
10、n 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 correct application. C
11、ompliance 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 displayed in this d
12、ocument indicates when the document was last issued.ISO 5725-6:1994 ii BSI 09 May 2002 Contents Page Foreword iv Introduction 1 1S c o p e 1 2 Normative references 2 3 Definitions 2 4 Determination of limits 2 4.1 Repeatability and reproducibility limits 2 4.2 Comparisons based on more than two valu
13、es 3 5 Methods for checking the acceptability of test results and determining the final quoted result 5 5.1 General 5 5.2 Methods for checking the acceptability of test results obtained under repeatability conditions 5 5.3 Methods for checking the acceptability of test results obtained under both re
14、peatability and reproducibility conditions 12 6 Method for checking the stability of test results within a laboratory 14 6.1 Background 14 6.2 Methods for checking stability 15 7 Use of repeatability and reproducibility standard deviations in assessing laboratories 30 7.1 Assessment method 30 7.2 Ev
15、aluation of the use of a measurement method by a laboratory not previously assessed 30 7.3 Continued assessment of previously approved laboratories 34 8 Comparison of alternative measurement methods 39 8.1 Origin of alternative measurement methods 39 8.2 Purpose of comparing measurement methods 39 8
16、.3 Method B is a candidate for an alternative standard method (“Standardization experiment” not defined) 39 8.4 Accuracy experiment 40 8.5 Method B is a candidate for a routine method 46 Annex A (normative) Symbols and abbreviations used in ISO 5725 48 Figure 1 Method for checking the acceptability
17、of test results, obtained under repeatability conditions, when two test results are obtained to start with and obtaining test results is inexpensive: Case 5.2.2.1 7 Figure 2 Method for checking the acceptability of test results, obtained under repeatability conditions, when two test results are obta
18、ined to start with and obtaining test results is expensive: Case 5.2.2.2a) 8 Figure 3 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 5.2.2.2b) 9ISO 5725-6:1
19、994 BSI 09 May 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 A 10 Figure 5 Method for checking the acceptability of test results, ob
20、tained under repeatability conditions, when n test results are obtained to start with and obtaining test results is expensive: Case B 10 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
21、 and obtaining test results is expensive: Case C 11 Figure 7 Range chart for the nickel content (%) of a private reference material, obtained under repeatability conditions 19 Figure 8 Range chart for the sulfur content (%) in blast-furnace coke, obtained under time-and-operator-different intermedia
22、te precision conditions 21 Figure 9 Shewhart control chart for of the ash content % (m/m) of a private reference material 25 Figure 10 Cumulative sum control chart for of the ash content % (m/m) of a private reference material 26 Figure 11 Shewhart control chart for of the As content for the silver
23、diethyldithiocarbamate-arsine evolution colorimetric procedure for arsenic in zinc oxide 27 Figure 12 Cumulative sum control chart for of the As contentfor the silver diethyldithiocarbamate-arsine evolution colorimetric procedure for arsenic in zinc oxide 27 Table 1 Critical range factors, f(n) 6 Ta
24、ble 2 Values of c(n)1 4 Table 3 Classification for characteristics of test materials according to their true values and important parameters for checking accuracy (trueness and precision) of results 16 Table 4 Factors for computing a range chart 17 Table 5 Control chart data sheet for example 1 (6.2
25、.2)1 8 Table 6 Control chart data sheet for example 2 (6.2.3)2 2 Table 7 Control chart data sheet for example 3 (6.2.4)2 4 Table 8 -chart data sheet for example 4 (6.2.5)2 9 Table 9 Cement content of concrete 32 Table 10 Cell means and ranges 32 Table 11 Alkalinity of water 36 Table 12 Cell means of
26、 Table 11 36 Table 13 Cell ranges of Table 11 37 Table 14 Values of (v A , v B , , ) or (v A , v B , , ) for = 0,05 and = 0,05 42 x x xISO 5725-6:1994 iv BSI 09 May 2002 Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO memb
27、er 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 right to be represented on that committee. International organizations, government
28、al 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 International Standards adopted by the technical committees are circulated to the memb
29、er 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, Applications of statistical methods, Subcommittee SC 6, Measurement methods and resu
30、lts. 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 determination of repeatability and reproducibility of a standard measurement method; P
31、art 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 determination of the precision of a standard measurement method; Part 6: Use in practice o
32、f 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 repeatability and reproducibility conditions). Annex A forms an integral part of this part
33、 of ISO 5725.ISO 5725-6:1994 BSI 09 May 2002 1 Introduction 0.1 ISO 5725 uses two terms “trueness” and “precision” 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
34、reference value. “Precision” refers to the closeness of agreement between test results. 0.2 The need to consider “precision” arises because tests performed on presumably identical materials in presumably identical circumstances do not, in general, yield identical results. This is attributed to unavo
35、idable random errors inherent in every measurement procedure; the factors that influence the outcome of a measurement 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 r
36、esult and some specified value may be within the scope of unavoidable random errors, in which case a real deviation 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 differenc
37、e between them can be attributed to the inherent variation in the measurement procedure. 0.3 Parts 1 to 5 of ISO 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 th
38、e trueness (in terms of the various components of bias) of measurements produced by a standard measurement method. 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,
39、 this part of ISO 5725 applies that knowledge in practical situations in such a way as to facilitate commercial 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 accurac
40、y data can be used in various practical situations by: a) giving a standard method of calculating the repeatability 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 o
41、f test results obtained under repeatability or reproducibility conditions; c) describing how to assess the stability 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
42、given laboratory is able to use a given standard measurement method in a satisfactory way; e) describing how to 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 numeri
43、cal figure as the result, although this single figure may be the outcome of a calculation from a set of observations. 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
44、 the field of application will be given at the beginning of each particular application.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 publicatio
45、n, 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 curr
46、ently 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 (true
47、ness 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 (trueness and precision) of measurement methods and results Part 3: Intermediate measures of the precisio
48、n of a standard measurement method. ISO 5725-4:1994, Accuracy (trueness and precision) of measurement methods and results Part 4: Basic methods for the determination of the trueness of a standard measurement method. ISO 8258:1991, Shewhart control charts. ISO Guide 33:1989, Uses of certified referen
49、ce materials. ISO Guide 35:1989, Certification of reference materials General and statistical principles. ISO/IEC Guide 25:1990, General requirements for the competence of calibration and testing laboratories. 3 Definitions For the purposes of this part of ISO 5725, the definitions given in ISO 3534-1 and ISO 5725-1 apply. The symbols used in ISO 5725 are given in Annex A. 4 Determination of limits 4.1 Repeatability and reproducibility limits 4.1.1 In ISO 5725-
