ISO INTERNATIONAL STANDARD 11929-1 Second edition 2019-02 Determination of the characteristic limits (decision threshold, detection limit and limits of the coverage interval) for measurements of ionizing radiation Fundamentals and application - Part 1: Elementary applications Determination des limites caracteristiques (seuil dedécision,limite de détection et extrémites de I'intervalleelargi)pourmesurages de rayonnements ionisantsPrincipes fondamentaux et applications Partie1:Applicationsélémentaires Referencenumber ISO11929-1:2019(E) @IS0 2019 IS0 11929-1:2019(E) COPYRIGHTPROTECTEDDOCUMENT @ISO2019 All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either IsO at the address below orIso's memberbody in the countryof therequester. ISO copyright office CP 401 : Ch. de Blandonnet 8 CH-1214 Vernier, Geneva Phone:+41227490111 Fax:+4122749 09 47 Email: [email protected] Website: www.iso.org Published in Switzerland ii @ IS0 2019- All rights reserved IS011929-1:2019(E) Contents Page Foreword ..iv Introduction. ..V 1 Scope. ..1 2 Normative references .. 3 Terms and definitions ..2 4 Quantities and symbols ..6 5 Summary of procedures for evaluating a measurement and calculating the characteristiclimits 5.1 Generalaspects ..8 5.2 Modellingthemeasurement .9 5.3 General considerations about the applicability of the ISo/IEC Guide 98-3 .9 5.4 Evaluating the input quantities, standard uncertainties and covariances, and the primaryresultanditsassociatedstandarduncertainty .10 5.5 Evaluating the standard uncertainty as a function of an assumed true value of the measurand .10 5.6 Calculating the decision threshold and decisions to be made ..11 5.7 Calculating the detection limit and assessment of the measurement procedure ..12 5.8 Calculating a coverage interval for the measurand 12 5.9 Calculating the best estimate of the measurand and its associated standard uncertainty 13 5.10 Reporting the results... 14 6 Fundamentals and evaluation ofthe measurement .16 6.1 General aspects concerning the measurand. .16 6.2 Model of evaluation.. .16 6.2.1 General model. ..16 6.2.2 Model inionizingradiation counting measurements ..17 6.3 Evaluation oftheprimarymeasurement result .18 6.4 Standard uncertaintyassociated with theprimary measurement result. .18 Standard uncertainty as afunction of an assumedvalue ofthemeasurand .19 8 Decisionthreshold, detection limitand assessments .21 8.1 Specifications 21 8.2 Decision threshold .21 8.3 Detection limit. 21 8.4 Assessments .22 9 Limits of the coverage interval .23 9.1 General aspects .23 9.2 The probabilistically symmetric coverage interval .23 9.3 The shortest coverage interval .24 10 The best estimate and its associated standard uncertainty .24 11 Documentation. ..25 AnnexA (normative)Repeated countingmeasurements with randominfluences ..26 AnnexB(normative)Measurementswithratemeters ..31 AnnexC(informative)Calculationofthedetectionlimitbyiteration ..33 AnnexD(informative)Calculationswithageneralizednetcountrate ..35 Annex E (informative)Distribution function of the standardized normal distribution ..38 Bibliography ..40 @IS0 2019-All rights reserved iii