ISO 29201-2012 Water quality - The variability of test results and the uncertainty of measurement of microbiological enumeration methods《水质 实验结果可变性及微生物计数法的测量不确定.pdf
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1、 ISO 2012 Water quality The variability of test results and the uncertainty of measurement of microbiological enumeration methods Qualit de leau - Variabilit des rsultats dessais et incertitude de mesure des mthodes dnumration microbienne INTERNATIONAL STANDARD ISO 29201 First edition 2012-01-15 Ref
2、erence number ISO 29201:2012(E) ISO 29201:2012(E) ii ISO 2012 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2012 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, including photocop
3、ying 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 Published in Switzer
4、land ISO 29201:2012(E) ISO 2012 All rights reserved iii Contents Page Foreword . v Introduction .vi 1 Scope 1 2 Key concepts 1 2.1 Uncertainty of measurement 1 2.2 Estimation of the uncertainty of measurement . 1 2.3 Intralaboratory reproducibility . 2 2.4 Combined standard uncertainty 2 2.5 Relativ
5、e standard uncertainty 2 2.6 Relative variance . 3 2.7 Expanded uncertainty and expanded relative uncertainty 3 3 Microbiological methods . 4 3.1 Common basis . 4 3.2 Quantitative instruments . 4 3.3 Uncertainty structure . 4 3.4 Expression of combined uncertainty . 4 4 Choices of approach 5 4.1 Gen
6、eral . 5 4.2 Choices of evaluation approach . 6 4.3 Choices of expression and use of measurement uncertainty 7 5 The component approach to the evaluation of operational uncertainty 7 5.1 General . 7 5.2 Identification of the components of uncertainty . 7 5.3 Evaluation 7 6 The global approach to the
7、 determination of the operational uncertainty 8 6.1 General . 8 6.2 Evaluation 9 7 Combined uncertainty of the test result .10 7.1 Basic principle .10 7.2 Operational variability 10 7.3 Intrinsic variability .10 7.4 Combined uncertainty 10 7.5 Borderline cases 10 Annex A (informative) Symbols and de
8、finitions . 11 Annex B (normative) General principles for combining components of uncertainty 13 Annex C (normative) Intrinsic variability Relative distribution uncertainty of colony counts .18 Annex D (normative) Intrinsic variability of most probable number estimates .20 Annex E (normative) Intrin
9、sic variability (standard uncertainty) of confirmed counts .23 Annex F (normative) Global approach for determining the operational and combined uncertainties .26 Annex G (normative) Component approach to evaluation of the combined relative uncertainty under intralaboratory reproducibility conditions
10、 .31 Annex H (normative) Experimental evaluation of subsampling variance .35 Annex I (normative) Relative repeatability and intralaboratory reproducibility of volume measurements .38 Annex J (normative) Relative uncertainty of a sum of test portions 40 Annex K (normative) Relative uncertainty of dil
11、ution factor F 44 ISO 29201:2012(E) iv ISO 2012 All rights reserved Annex L (normative) Repeatability and intralaboratory reproducibility of counting .46 Annex M (normative) Incubation effects Uncertainty due to position and time .50 Annex N (informative) Expression and use of measurement uncertaint
12、y 55 Bibliography .61 ISO 29201:2012(E) Foreword 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 bo
13、dy interested 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 Electrot
14、echnical 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 b
15、y 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. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent ri
16、ghts. ISO shall not be held responsible for identifying any or all such patent rights. ISO 29201 was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 4, Microbiological methods. ISO 2012 All rights reserved v ISO 29201:2012(E) Introduction Testing laboratories are required
17、to apply procedures for estimating uncertainty of measurement (see ISO/IEC 17025 5 ). Without such an indication, measurement results cannot be compared, either among themselves or with reference values (see ISO/IEC Guide 98-3:2008 7 ). General guidelines for the evaluation and expression of uncerta
18、inty in measurement have been elaborated by experts in physical and chemical metrology, and published by ISO and IEC in ISO/IEC Guide 98-3:2008. 7However, ISO/IEC Guide 98-3:2008 7does not address measurements in which the observed values are counts. The emphasis in ISO/IEC Guide 98-3:2008 7is on th
19、e “law of propagation of uncertainty” principle, whereby combined estimates of the uncertainty of the final result are built up from separate components evaluated by whatever means are practical. This principle is referred to as the “component approach” in this International Standard. It is also kno
20、wn as the “bottom-up” or “step-by-step” approach. It has been suggested that the factors that influence the uncertainty of microbiological enumerations are not well enough understood for the application of the component approach (see ISO/TS 19036:2006 6 ). It is possible that this approach underesti
21、mates the uncertainty because some significant uncertainty contributions are missed. Reference 19 shows, however, that the concepts of ISO/IEC Guide 98-3:2008 7are adaptable and applicable to count data as well. Another principle, a “black-box” approach known as the “top-down” or “global” approach,
22、is based on statistical analysis of series of repeated observations of the final result (see ISO/TS 19036:2006 6 ). In the global approach it is not necessary to quantify or even know exactly what the causes of uncertainty in the black box are. According to the global philosophy, once evaluated for
23、a given method applied in a particular laboratory, the uncertainty estimate may be reliably applied to subsequent results obtained by the method in the same laboratory, provided that this is justified by the relevant quality control data (EURACHEM/CITAC CG 4 10 ). Every analytical result produced by
24、 a given method thus should have the same predictable uncertainty. This statement is understandable against its background of chemical analysis. In chemical analyses the uncertainty of the analytical procedure and the uncertainty of the final result of analysis are usually the same. The global princ
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