1、 Reference number ISO/TR 24697:2011(E) ISO 2011TECHNICAL REPORT ISO/TR 24697 First edition 2011-08-15 Textiles and textile products Guidelines on the determination of the precision of a standard test method by interlaboratory trials Textiles et produits textiles Lignes directrices pour la dterminati
2、on de la fidlit dune mthode dessai normalise au moyen dessais dinterlaboratoires ISO/TR 24697:2011(E) COPYRIGHT PROTECTED DOCUMENT ISO 2011 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical
3、, including photocopying and microfilm, without permission in writing from either ISO at the address below 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
4、Published in Switzerland ii ISO 2011 All rights reservedISO/TR 24697:2011(E) ISO 2011 All rights reserved iiiContents Page Foreword iv Introduction . v 1 Scope 1 2 Normative references 1 3 Terms and definitions . 1 4 Requirements for an interlaboratory precision trial 2 4.1 General . 2 4.2 Personnel
5、 requirements . 3 4.3 Laboratory requirements 3 4.4 Sample requirements 3 4.5 Organization of the interlaboratory trial 3 4.6 Conducting the interlaboratory trial 4 4.7 Analysis of the results 4 Annex A (informative) Form examples . 5 Annex B (informative) Statistical assessment . 7 ISO/TR 24697:201
6、1(E) iv ISO 2011 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 i
7、nterested in 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 Electrotechn
8、ical Commission (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 th
9、e 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. In exceptional circumstances, when a technical committee has collected data of a different kind from that which is n
10、ormally published as an International Standard (“state of the art”, for example), it may decide by a simple majority vote of its participating members to publish a Technical Report. A Technical Report is entirely informative in nature and does not have to be reviewed until the data it provides are c
11、onsidered to be no longer valid or useful. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO/TR 24697 was prepared by Technical Committee ISO/TC 38
12、, Textiles, Subcommittee SC 24, Conditioning atmospheres and physical tests for textile fabrics. ISO/TR 24697:2011(E) ISO 2011 All rights reserved vIntroduction It is well known that developing a standardized test method is not always an easy task. Most of the effort involves going through lots of d
13、etails and trying to reach agreement between all the parties involved. As a consequence, it is wise to also dedicate part of the job to define what level of reliability the result of the standardized test method will have once it is applied. The participation of interested laboratories is welcome, p
14、ossibly those having a delegate in the commission in charge of developing the standardized test method. Following this consideration, the aim of this Technical Report is to supply guidelines in case there is an intention to evaluate the uncertainty of that standardized test method by carrying out in
15、terlaboratory tests. TECHNICAL REPORT ISO/TR 24697:2011(E) ISO 2011 All rights reserved 1Textiles and textile products Guidelines on the determination of the precision of a standard test method by interlaboratory trials 1 Scope This Technical Report can be applied to textiles and textile products an
16、d is concerned only with test methods which operate in a continuous scale to yield a single numerical figure as the test result. However, this single figure can be the outcome of a calculation from a set of measurements. The distribution of test results is required to be unimodal and is assumed to b
17、e normal. With non-Gaussian distributions, other evaluation procedures will be necessary. It does not cover methods which yield discrete values, pass/fail (go/no go) type results, (accept/reject) tests or where a ranking scheme is in operation. 2 Normative references The following referenced documen
18、ts are indispensable for the 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 3534-1, Statistics Vocabulary and symbols Part 1: General statistical terms a
19、nd terms used in probability ISO 5725-2, 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 5725-6, Accuracy (trueness and precision) of measurement methods and resu
20、lts Part 6: Use in practice of accuracy values 3 Terms and definitions For the purposes of this document, the terms and definitions in ISO 3534-1, ISO 5725-2 and ISO 5725-6 and the following apply. 3.1 observed value value of a characteristic obtained as a result of a single observation 3.2 test res
21、ults value of a characteristic obtained by carrying out a specified test method NOTE The test method should specify that a number of individual observations to be made and their average and other appropriate function (such as the median and the indication of the dispersion measured by a standard dev
22、iation) be reported as the test result. ISO/TR 24697:2011(E) 2 ISO 2011 All rights reserved3.3 level of the test in a precision experiment general average of the test results from all laboratories for one particular material or specimen tested 3.4 cell in precision experiment test results at a singl
23、e level obtained by one laboratory 3.5 precision closeness of agreement between independent test results obtained under stipulated conditions such that they are not influenced by any previous result on the same or similar material NOTE The measure of precision is usually expressed as, or derived fro
24、m, a standard deviation, which is a measure of imprecision computed from the test data. Less precision is reflected by a larger standard deviation. 3.6 accuracy closeness of agreement between a test result and the accepted reference value 3.7 trueness closeness of agreement between the average value
25、 from a large series of test results and an accepted reference value 3.8 repeatability measure of the dispersion of test results under conditions where test results are obtained with the same method on identical test material in the same laboratory by the same operator using the same equipment withi
26、n short intervals of time 3.9 reproducibility measure of the dispersion of test results under conditions where test results are obtained with the same method on the same test material in different laboratories with different operators using different equipment 3.10 outlier member of a set of values
27、which is inconsistent with the other members of that set 3.11 degree of freedom number of independent observations NOTE In the evaluation of a test method, an absolute minimum of five laboratories should be used from at least three different countries. 4 Requirements for an interlaboratory precision
28、 trial 4.1 General For a successful trial it is required that: The participating laboratories and personnel are given all the details before the start of the exercise; All participating laboratories keep to the instructions for carrying out the experiment; All operators are familiar with the test me
29、thod; ISO/TR 24697:2011(E) ISO 2011 All rights reserved 3 All measurements taken shall be reported; It is not acceptable to carry out more than the number of replicates specified; It is not acceptable to report the mean of a series of replicates as a single observed value. 4.2 Personnel requirements
30、 4.2.1 The project manager The working group or committee shall appoint a Project Manager by one of its members who will take full responsibility for the organization of the experiment, supervise its execution, collation the results and determination the precision of the test method. The project man
31、ager should be fully familiar with the test method, and should have knowledge of statistical design and analysis. If necessary he may appoint a statistician to assist with the analysis of the results. 4.2.2 Laboratory contact person A suitable contact person the laboratory contact shall be identifie
32、d within each participating laboratory, to which the samples and information about the trial should be sent. This person is responsible for supervision of the testing by the operator(s) and for the reporting of results to the project manager. 4.2.3 The operator(s) In each of the participating labora
33、tories the trial must be performed by an operator who is competent in carrying out this sort of measurement. 4.3 Laboratory requirements In the evaluation of a test method, an absolute minimum of five laboratories should be used from at least three different countries. The participation of intereste
34、d laboratories is welcome; possibly those having a delegate in the commission in charge of developing the standardized test method. 4.4 Sample requirements 4.4.1 The number of types of material (levels) tested in each laboratory should be selected such that the total number of samples tested across
35、all laboratories is not less than 30, preferably nearer to 60. Thus, if there are 5 participating laboratories, a minimum of 6 materials (levels) are needed. 4.4.2 The working group should agree on the types of materials required to cover the whole field of application of the test (different levels)
36、. 4.4.3 The quantity of material prepared shall be sufficient to cover the trial, and to allow a reserve. 4.5 Organization of the interlaboratory trial The project manager is responsible for the organization of the trial as follows: 4.5.1 The design of the trial, based on ISO 5725-2, to include the
37、number of levels required (see 4.4.1), a number of times that the test should be carried out, and the order in which samples should be tested. 4.5.2 The preparation of sufficient samples and their randomization to ensure that each laboratory receives as nearly as possible homogeneous samples. Additi
38、onal samples shall be prepared for the replacement of any lost or damaged samples if necessary. ISO/TR 24697:2011(E) 4 ISO 2011 All rights reserved4.5.3 Labelling of samples Each sample should be labelled preferably with a three or five digit random number. The allocation of random numbers to the sa
39、mples should be known only to the Project Manager. Preparation of an instruction sheet for the participating laboratories to include, at least, the following: the test method to be used; the number of repeat measurements to be made; the number of operators to be used; to specify how the samples are
40、to be conditioned prior to the test; the order in which the samples should be tested; the deadline for completion of tests; the questionnaire for feed-back; the standard sheet for the reporting of the results (see Annex A, for an example). 4.5.4 Distribution of the samples and instructions to the la
41、boratories. 4.6 Conducting the interlaboratory trial 4.6.1 Testing should be carried out by the participating laboratories according to the instructions provided by the Project Manager. 4.6.2 Results should be sent back to the Project Manager within the required time-scale. Any deviations from the r
42、equired procedure or any problems experienced should be reported. 4.7 Analysis of the results 4.7.1 Data correction 4.7.1.1 Missing data Unless these are so excessive as to hazard the validity of the study, they should be ignored in the analysis apart from necessary procedural adjustments. 4.7.1.2 O
43、utliers Experience has taught that outliers cannot be avoided and have to be taken into consideration. As a general rule no readings should be rejected unless either, there is evidence for a definite source of error or, they fail some statistical criteria. It should be noted that not only individual
44、 results but data from a source (i.e. a laboratory) may be subject to this procedure. Under no circumstances, after rejection of outliers, may be a further analysis be undertaken to detect further outliers inconsistent with the adjusted data set. For an extensive treatment on the subject see ISO 572
45、5-2. 4.7.2 When the standards deviation for both repeatability and reproducibility do not show any dependence on the level of tests it is permissible to average the values before calculation of the precision. Otherwise, following suitable statistical test to check for homogeneity (see ISO 5725.2:199
46、4, Clause 7.3.3 - Cochrans test) separate precision values may be assigned to each level. 4.7.3 Calculation of precision See Annex B. ISO/TR 24697:2011(E) ISO 2011 All rights reserved 5Annex A (informative) Form examples Form A - Recommended form for the collation of the original data Laboratory Lev
47、el 1 Level 2 Level 3 Level 4 Level 5 Level 6 1 n 1 n k2 3 4 5 p n k : total number of replicates per cell Form B - Recommended form for collation of calculated averages Laboratory Level 1 Level 2 Level 3 Level 4 Level 5 Level 6 1 2 3 4 5 p ISO/TR 24697:2011(E) 6 ISO 2011 All rights reservedForm C -
48、Recommended form for collation of measured spread within cells Laboratory Level 1 Level 2 Level 3 Level 4 Level 5 Level 6 1 2 3 4 5 p Symbol used for laboratory i Symbol used for level j ISO/TR 24697:2011(E) ISO 2011 All rights reserved 7Annex B (informative) Statistical assessment B.1 Foreword It i
49、s assumed that this particular exercise of interlaboratory test is needed to give more reliability and better confidence on the action that the results of any type of test may suggest to undertake. This is particularly true when the final outcome of a normative is the completion of a test. It can be agreed upon the fact that dedicating only most effort in “assembling” a normative, with lots of details, finding agreement from all parts involved and not attaching to it some
