ISO INTERNATIONAL STANDARD 29201 First edition 2012-01-15 Water quality The variability of test results and the uncertainty of measurement of microbiological enumeration methods Qualité de I'eau - Variabilite des résultats d'essais et incertitude de mesure des methodes d'énumeration microbienne Reference number ISO 29201:2012(E) ISO @ISO2012 I by IHS under lic No reproduction or networking permitted without license from IHS Not for Resale ISO 29201:2012(E) COPYRiGHTPROTECTEDDOCUMENT 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 photocopying and microfilm, without permission in writing from either ISO at the address below or ISO's 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 [email protected] Web www.iso.org Published in Switzerland @ ISO 2012 - All rights reserved No reproduction or networking permtted without license from IHS Not for Resale ISO 29201:2012(E) Contents Page Foreword Introduction 1 Scope 2 Key concepts.. 2.1 Uncertainty of measurement 2.2 Estimation of the uncertainty of measurement.. 2.3 Intralaboratory reproducibility. 2.4 Combined standard uncertainty. 2.5 Relative standard uncertainty. 2.6 Relative variance 2.7 Expanded uncertainty and expanded relative uncertainty 3 Microbiological methods. 3.1 Common basis. 3.2 Quantitative instruments.. 3.3 Uncertainty structure 3.4 Expression of combined uncertainty 4 Choices of approach. 5 4.1 General. 4.2 Choices of evaluation approach 4.3 Choices of expression and use of measurement uncertainty 5 The component approach to the evaluation of operational uncertainty 5.1 General 5.2 Identificationofthecomponentsofuncertainty.. 5.3 Evaluation..... 6 The global approach to the determination of the operational uncertainty. 6.1 General.... 8 6.2 Evaluation. 9 Combined uncertainty of the test result, 10 7.1 Basic principle .. 10 7.2 Operationalvariability 10 7.3 Intrinsic variability. 10 7.4 Combined uncertainty. ..10 7.5 Borderline cases.. 10 Annex A (informative) Symbols and definitions. 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) Intrinsic 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. 31 Annex H (normative) Experimental evaluation of subsampling variance.. .35 Annex I (normative) Relative repeatability and intralaboratory reproducibility of volumemeasurements. .38 Annex J (normative) Relative uncertainty of a sum of test portions. .40 AnnexK(normative)Relativeuncertaintyofdilutionfactor 44 ili ed without license from IHS Not for Resale