BS ISO 11929-2010 Determination of the characteristic limits (decision threshold detection limit and limits of the confidence interval) for measurements of ionizing radiation - Fun.pdf

1、BS ISO11929:2010ICS 17.240NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDDetermination ofthe characteristiclimits (decisionthreshold, detectionlimit and limits of theconfidence interval)for measurements ofionizing radiation Fundamentals andapplicationThis Briti

2、sh Standard was published under the authority of the Standards Policy and Strategy Committee on 31 March 2010 BSI 2010ISBN 978 0 580 59044 3Amendments/corrigenda issued since publicationDate CommentsBS ISO 11929:2010National forewordThis British Standard is the UK implementation of ISO 11929:2010.It

3、 supersedes BS ISO 11929-1:2000, BS ISO 11929-2:2000, BS ISO 11929-3:2000, BS ISO 11929-4:2001, BS ISO 11929-5:2005, BS ISO 11929-6:2005, BS ISO 11929-7:2005 and BS ISO 11929-8:2005, which are withdrawn.The UK participation in its preparation was entrusted to Technical Committee NCE/2, Radiation pro

4、tection and measurement.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.Compliance with a British Standard cann

5、ot confer immunity from legal obligations.BS ISO 11929:2010Reference numberISO 11929:2010(E)ISO 2010INTERNATIONAL STANDARD ISO11929First edition2010-03-01Determination of the characteristic limits (decision threshold, detection limit and limits of the confidence interval) for measurements of ionizin

6、g radiation Fundamentals and application Dtermination des limites caractristiques (seuil de dcision, limite de dtection et extrmits de lintervalle de confiance) pour mesurages de rayonnements ionisants Principes fondamentaux et applications BS ISO 11929:2010ISO 11929:2010(E) PDF disclaimer This PDF

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10、SO 2010 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 ISOs member body in th

11、e 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 Switzerland ii ISO 2010 All rights reservedBS ISO 11929:2010ISO 11929:2010(E) ISO 2010 All rights reserved iiiContents

12、Page Foreword iv Introduction.v 1 Scope1 2 Normative references1 3 Terms and definitions .2 4 Quantities and symbols4 5 Fundamentals 5 5.1 General aspects concerning the measurand5 5.2 Model 6 5.3 Calculation of the standard uncertainty as a function of the measurand .8 6 Characteristic limits and a

13、ssessments .10 6.1 Specifications 10 6.2 Decision threshold 10 6.3 Detection limit10 6.4 Limits of the confidence interval .12 6.5 Assessment of a measurement result.13 6.6 Assessment of a measurement procedure.14 7 Documentation 15 Annex A (informative) Overview of the general procedure 16 Annex B

14、(normative) Various applications 18 Annex C (normative) Applications to counting spectrometric measurements25 Annex D (informative) Application examples.37 Annex E (informative) Distribution function of the standardized normal distribution 49 Annex F (informative) Explanatory notes .51 Bibliography5

15、9 BS ISO 11929:2010ISO 11929:2010(E) iv ISO 2010 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 technica

16、l 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, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely wit

17、h the International Electrotechnical 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 Inter

18、national Standards adopted by 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

19、 be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 11929 was prepared by Technical Committee ISO/TC 85, Nuclear energy, Subcommittee SC 2, Radiation protection. This first edition of ISO 11929 cancels and replaces ISO 11929-1:2000,

20、ISO 11929-2:2000, ISO 11929-3:2000, ISO 11929-4:2001, ISO 11929-5:2005, ISO 11929-6:2005, ISO 11929-7:2005 and ISO 11929-8:2005, which have been technically revised, specifically with reference to the type of statistical treatment of the data. BS ISO 11929:2010ISO 11929:2010(E) ISO 2010 All rights r

21、eserved vIntroduction The limits to be provided according to this International Standard by means of statistical tests and specified probabilities allow detection possibilities to be assessed for a measurand and for the physical effect quantified by this measurand as follows: the “decision threshold

22、” gives a decision on whether or not the physical effect quantified by the measurand is present; the “detection limit” indicates the smallest true value of the measurand which can still be detected with the applied measurement procedure; this gives a decision on whether or not the measurement proced

23、ure satisfies the requirements and is therefore suitable for the intended measurement purpose; the “limits of the confidence interval” enclose, in the case of the physical effect recognized as present, a confidence interval containing the true value of the measurand with a specified probability. Her

24、einafter, the limits mentioned are jointly called “characteristic limits”. Since measurement uncertainty plays an important part in this International Standard, the evaluation of measurements and the treatment of measurement uncertainties are carried out by means of the general procedures according

25、to ISO/IEC Guide 98-3; see also References 1, 2. This enables the strict separation of the evaluation of the measurements, on the one hand (Clause 5), and the provision and calculation of the characteristic limits, on the other hand (Clause 6). This International Standard is based on Bayesian statis

26、tics according to References 6 to 19, such that uncertain quantities and influences, which do not behave randomly in measurements repeated several times or in counting measurements, can also be taken into account. Equations are provided for the calculation of the characteristic limits of an ionizing

27、 radiation measurand via the “standard measurement uncertainty” of the measurand (hereinafter “standard uncertainty”). The standard uncertainties of the measurement, as well as those of sample treatment, calibration of the measuring system and other influences are taken into account. However, the la

28、tter standard uncertainties are assumed to be known from previous investigations. BS ISO 11929:2010BS ISO 11929:2010INTERNATIONAL STANDARD ISO 11929:2010(E) ISO 2010 All rights reserved 1Determination of the characteristic limits (decision threshold, detection limit and limits of the confidence inte

29、rval) for measurements of ionizing radiation Fundamentals and application 1 Scope This International Standard specifies a procedure, in the field of ionizing radiation metrology, for the calculation of the “decision threshold”, the “detection limit” and the “limits of the confidence interval” for a

30、non-negative ionizing radiation measurand, when counting measurements with preselection of time or counts are carried out, and the measurand results from a gross count rate and a background count rate as well as from further quantities on the basis of a model of the evaluation. In particular, the me

31、asurand can be the net count rate as the difference of the gross count rate and the background count rate, or the net activity of a sample. It can also be influenced by calibration of the measuring system, by sample treatment and by other factors. This International Standard also applies, in the sam

32、e way to: counting measurements on moving objects (see B.2); measurements with linear-scale analogue count rate measuring instruments (hereinafter called ratemeters, see B.3); repeated counting measurements with random influences (see B.4); counting measurements on filters during accumulation of rad

33、ioactive material (see B.5); counting spectrometric multi-channel measurements, if particular lines in the spectrum are to be considered and no adjustment calculations, for instance, an unfolding, have to be carried out (see C.2 to C.4); counting spectrometric multi-channel measurements if evaluated

34、 by unfolding methods (see C.5), in particular, alpha- and gamma-spectrometric measurements (see C.5.5 and C.5.6, respectively). This International Standard also applies analogously to other measurements of any kind if the same model of the evaluation is involved. In this sense, it is also applicabl

35、e to measurements with albedo dosimeters 18. Further practical examples can be found in other International Standards, for example ISO 1858921, ISO 969622, ISO 969723, ISO 969824, ISO 969925, ISO 1070326, ISO 750327and ISO 2821828. 2 Normative references The following referenced documents are indisp

36、ensable 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 31-0, Quantities and units Part 0: General principles ISO 31-9, Quantities and units Part

37、9: Atomic and nuclear physics BS ISO 11929:2010ISO 11929:2010(E) 2 ISO 2010 All rights reservedISO/IEC Guide 98-3:2008, Uncertainty of measurement Part 3: Guide to the expression of uncertainty in measurement (GUM:1995) ISO/IEC Guide 99:2007, International vocabulary of metrology Basic and general c

38、oncepts and associated terms (VIM) ISO 3534-1, Statistics Vocabulary and symbols Part 1: General statistical terms and terms used in probability 3 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 31-0, ISO 31-9, ISO/IEC Guide 98-3, ISO/IEC Guide 99 and

39、ISO 3534-1 and the following apply. 3.1 measurement procedure set of operations, described specifically, used in the performance of particular measurements according to a given method ISO/IEC Guide 99:2007, 2.6 3.2 measurand particular quantity subject to measurement ISO/IEC Guide 99:2007, 2.3 NOTE

40、In this International Standard, a measurand is non-negative and quantifies a nuclear radiation effect. The effect is not present if the true value of the measurand is zero. An example of a measurand is the intensity of an energy line in a spectrum above the background in a spectrometric measurement.

41、 3.3 result of a measurement value attributed to a measurand, obtained by measurement ISO/IEC Guide 99:2007, 2.9 3.4 uncertainty of measurement uncertainty non-negative parameter, which characterizes the dispersion of the values which could reasonably be attributed to the measurand ISO/IEC Guide 99:

42、2007, 2.26 See also ISO/IEC Guide 98-3. NOTE The uncertainty of a measurement derived according to ISO/IEC Guide 98-3 comprises, in general, many components. Some of these components can be evaluated from the statistical distribution of the results of series of measurements and can be characterized

43、by experimental standard deviations. The other components, which can also be characterized by standard deviations, are evaluated from assumed or known probability distributions based on experience and other information. 3.5 model of evaluation set of mathematical relationships between all measured a

44、nd other quantities involved in the evaluation of measurements NOTE The model of evaluation does not need to be an explicit function; it can also be an algorithm realized by a computer code. BS ISO 11929:2010ISO 11929:2010(E) ISO 2010 All rights reserved 33.6 decision threshold value of the estimato

45、r of the measurand, which when exceeded by the result of an actual measurement using a given measurement procedure of a measurand quantifying a physical effect, one decides that the physical effect is present NOTE 1 The decision threshold is defined such that in cases where the measurement result, y

46、, exceeds the decision threshold, ,y* the probability that the true value of the measurand is zero is less or equal to a chosen probability, . NOTE 2 If the result, y, is below the decision threshold, ,y* the result cannot be attributed to the physical effect; nevertheless it cannot be concluded tha

47、t it is absent. 3.7 detection limit smallest true value of the measurand which ensures a specified probability of being detectable by the measurement procedure NOTE With the decision threshold according to 3.6, the detection limit is the smallest true value of the measurand for which the probability

48、 of wrongly deciding that the true value of the measurand is zero is equal to a specified value, , when, in fact, the true value of the measurand is not zero. 3.8 limits of the confidence interval values which define a confidence interval containing the true value of the measurand with a specified p

49、robability NOTE A confidence interval is sometimes known as a credible interval or a Bayesian interval. It is characterized in this International Standard by a specified probability (1 ) . 3.9 best estimate of the true value of the measurand expectation value of the probability distribution of the true value of the measurand, given the experimental result and all prior information on the measurand NOTE The best estimate, among all possible estimates of the measurand on the basis