1、BRITISH STANDARD BS ISO 11843-4:2003 Capability of detection Part 4: Methodology for comparing the minimum detectable value with a given value ICS 03.120.30; 17.020 BS ISO 11843-4:2003 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 21 Novemb
2、er 2003 BSI 21 November 2003 ISBN 0 580 42956 3 National foreword This British Standard reproduces verbatim ISO 11843-4:2003 and implements it as the UK national standard. The UK participation in its preparation was entrusted to Technical Committee SS/6, Precision of test methods, which has the resp
3、onsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international publications referred to in this document may be found in the BSI Catalogue under the section entitled “International
4、 Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. 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 St
5、andard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and Euro
6、pean developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the ISO title page, pages ii to iv, pages 1 to 8, an inside back cover and a back cover. The BSI copyright notice displayed in this document indicates when the document was
7、 last issued. Amendments issued since publication Amd. No. Date Comments Reference number ISO 11843-4:2003(E) OSI 3002INTERNATIONAL STANDARD ISO 11843-4 First edition 2003-11-01 Capability of detection Part 4: Methodology for comparing the minimum detectable value with a given value Capacit de dtect
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13、ISO 3002 Allr ihgtsser edevrBSISO118434:2003IS-34811 O4:(3002E) I SO 3002 All irhgts seredevr iiiForeword 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 car
14、ried out through ISO technical 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.
15、 ISO collaborates closely with 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 Interna
16、tional Standards. Draft International 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
17、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 11843-4 was prepared by Technical Committee ISO/TC 69, Applications of statistical methods, Subcommittee SC 6, Measurement methods and results. ISO 1184
18、3 consists of the following parts, under the general title Capability of detection: Part 1: Terms and definitions Part 2: Methodology in the linear calibration case Part 3: Methodology for determination of the critical value for the response variable when no calibration data are used Part 4: Methodo
19、logy for comparing the minimum detectable value with a given value BSISO118434:2003IS-34811 O4:(3002E) iv I SO 3002 All irhgts seredevrIntroduction An ideal requirement for the capability of detection with respect to a selected state variable would be that the actual state of every observed system c
20、an be classified with certainty as either equal to or different from its basic state. However, due to systematic and random variations, this ideal requirement cannot be satisfied for the following reasons. a) In reality all reference states, including the basic state, are never known in absolute ter
21、ms of the state variable. Hence, all states can only be characterized correctly in terms of differences from the basic state, i.e. in terms of the net state variable. b) In order to prevent erroneous decisions, it is generally recommended to report differences from the basic state only, i.e. data in
22、 terms of the net state variable. NOTE In ISO Guide 30 and in ISO 11095, no distinction is made between the state variable and the net state variable. As a consequence, in those two documents reference states are without justification assumed to be known with respect to the state variable. c) Furthe
23、rmore, the calibration and the processes of sampling and preparation add random variation to the measurement results. In this part of ISO 11843 the probability is of detecting (erroneously) that a system is not in the basic state when it is in the basic state; the probability is of (erroneously) not
24、 detecting that a system, for which the value of the net state variable is equal to the minimum detectable value (x d ) is not in the basic state. BSISO118434:2003INTENRATIONAL TSANDADR IS-34811 O4:(3002E)I SO 3002 All irhgts seredevr 1Capability of detection Part 4: Methodology for comparing the mi
25、nimum detectable value with a given value 1 Scope This part of ISO 11843 deals with the assessment of the capability of detection of a measurement method without the assumptions in ISO 11843-2 of a linear calibration curve and certain relationships between the residual standard deviation and the val
26、ue of the net state variable NOTE These assumptions are often doubtful for values of the net state variable close to zero. Instead of estimating the minimum detectable value, this part of ISO 11843 provides a criterion for judging whether the minimum detectable value is less than a given level of th
27、e net state variable, and the basic experimental design for testing the conformity of this criterion. For assessment of the capability of detection, for instance as part of the validation of a measurement method, it is often sufficient to confirm that the method has a minimum detectable value that i
28、s less than a given value. 2 Normative references The following referenced documents 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.
29、 ISO 3534-1, Statistics Vocabulary and symbols Part 1: Probability and general statistical terms ISO 3534-2: 1) , Statistics Vocabulary and symbols Part 2: Applied statistics ISO 3534-3:1999, Statistics Vocabulary and symbols Part 3: Design of experiments ISO 5479:1997, Statistical interpretation of
30、 data Tests for departure from normal distribution ISO 5725-2:1994, 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 11095:1996, Linear calibration using reference
31、 materials ISO 11843-1:1997, Capability of detection Part 1: Terms and definitions ISO Guide 30:1992, Terms and definitions used in connection with reference materials 1) To be published. (Revision of ISO 3534-2:1993) BSISO118434:2003IS-34811 O4:(3002E) 2 I SO 3002 All irhgts seredevr3 Terms and def
32、initions For the purposes of this document, the terms and definitions given in ISO 3534 (all parts), ISO 5479, ISO 5725-2, ISO 11095, ISO 11843-1 and ISO Guide 30 apply. 4 Experimental design 4.1 General The measurement method is assumed to be standardized. The same complete method shall be used for
33、 all measurements, whether of the reference states or of actual states (test samples). 4.2 Choice of reference states and reference materials The reference states shall include two values of the net state variable the value zero of the net state variable (i.e. in analytical chemistry, a sample of th
34、e blank material), and a given value, x g , which will be tested to determine whether it is greater than the minimum detectable value. The composition of the reference materials representing the reference states should be as close as possible to the composition of the material to be measured in orde
35、r to satisfy the requirement that reference and test materials behave in the same way in the measuring system. 4.3 Number of replications It is assumed that the capability of detection is assessed in a separate experiment with the same number of replications for both reference states specified in 4.
36、2. In an application of the method, measurements are performed for the reference material (representing the value zero of the net state variable) and the actual state. The number of replications used in applications of the method are usually smaller than the number of replications used in the assess
37、ment of the capability of detection of the method. The following notations are used: J is the number of replications of measurements on the reference material representing the value zero of the net state variable (blank sample) in an application of the method; K is the number of replications of meas
38、urements on the actual state (test sample) in an application of the method. N is the number of replications of measurements on each reference material (see 4.2) in assessment of the capability of detection; The value of N should preferably be at least 5. NOTE In validation of a method, the capabilit
39、y of detection is usually determined for J = K = 1. 5 The criterion for sufficient capability of detection 5.1 Basic assumptions Basic assumptions in this part of ISO 11843 are the measurements of the response variable of all materials are assumed to be independent and normally distributed, and the
40、reference and test materials behave in the same way in the measurement system. BSISO118434:2003IS-34811 O4:(3002E) I SO 3002 All irhgts seredevr 35.2 Critical value of the response variable When a test of the hypothesis that the net state variable of a test sample is zero is based on a comparison (i
41、n a randomized experiment) of the responses of the test sample and a sample in the basic state (blank sample known to have the net state variable equal to zero), the critical value of the response for the test sample (the mean of K measurements) is given by cb1b 11 yyz J K =+ + (1) The meanings of t
42、he symbols used here and in the rest of this part of ISO 11843 are given in Annex A. When the response variable decreases with increasing level of the net state variable, the critical value of the response is given by cb1b 11 yyz J K = + (2) where y cnow is a lower limit. In this situation, the expr
43、essions g band gb y y in 5.3, 5.4 and Clause 6 are changed to b gand bg y y respectively. 5.3 Probability of detecting a given value of the net state variable Instead of estimating the minimum detectable value of the net state variable (i.e. the value of the net state variable for which the power of
44、 the test in 5.2 has a specified value 1 ), this part of ISO 11843 provides a criterion for the power to be greater than or equal to 1 for a given value, x g , of the net state variable. If this criterion is satisfied, it may be concluded that the minimum detectable value is less than or equal to x
45、g . If the standard deviation of the response for a given value x gof the net state variable is g , the criterion for the power to be greater than or equal to 1 is given by 22 gb1b 1 b g 11 1 1 zz JK J K + + W (3) where band gare the expected values under the actual performance conditions for the re
46、sponses of the basic state and a sample with the net state variable equal to x g . NOTE Criterion (3) follows from the definition of net state variable and Figure 1 of ISO 11843-1:1997. With = , K = J and under the assumption that gW b(it is unusual for the standard deviation to decrease as the net
47、state variable increases), the criterion is simplified to gb 1 22 bg 2z J + W (4) 5.4 Confirmation of the criterion for sufficient capability of detection The standard deviations and expected values of the responses in Criterion (3) are usually unknown and the fulfilment of the criterion has to be c
48、onfirmed from experimental data. Thus, the expression on the left-hand side of the simplified Criterion (4) is an unknown constant, while the expression on the right-hand side is a known constant. BSISO118434:2003IS-34811 O4:(3002E) 4 I SO 3002 All irhgts seredevrFrom a validation experiment with N
49、observations of the responses for the basic state and a sample with the net state variable equal to x g , the expression on the left-hand side of Criterion (4) is estimated by gb 22 bg yy s s +(5) where the meanings for the symbols are as given in Annex A. An approximate 100(1) % lower confidence limit (CL) for (
