1、 Collection of SANS standards in electronic format (PDF) 1. Copyright This standard is available to staff members of companies that have subscribed to the complete collection of SANS standards in accordance with a formal copyright agreement. This document may reside on a CENTRAL FILE SERVER or INTRA
2、NET SYSTEM only. Unless specific permission has been granted, this document MAY NOT be sent or given to staff members from other companies or organizations. Doing so would constitute a VIOLATION of SABS copyright rules. 2. Indemnity The South African Bureau of Standards accepts no liability for any
3、damage whatsoever than may result from the use of this material or the information contain therein, irrespective of the cause and quantum thereof. ISBN 978-0-626-23474-4 SANS 11843-4:2009Edition 1 ISO 11843-4:2003Edition 1 SOUTH AFRICAN NATIONAL STANDARD Capability of detection Part 4: Methodology f
4、or comparing the minimum detectable value with a given value This national standard is the identical implementation of ISO 11843-4:2003 and is adopted with the permission of the International Organization for Standardization. Published by SABS Standards Division 1 Dr Lategan Road Groenkloof Private
5、Bag X191 Pretoria 0001Tel: +27 12 428 7911 Fax: +27 12 344 1568 www.sabs.co.za SABS SANS 11843-4:2009 Edition 1 ISO 11843-4:2003 Edition 1 Table of changes Change No. Date Scope National foreword This South African standard was approved by National Committee SABS TC 169, Applications of statistical
6、methods, in accordance with procedures of the SABS Standards Division, in compliance with annex 3 of the WTO/TBT agreement. This SANS document was published in September 2009. Reference numberISO 11843-4:2003(E)ISO 2003INTERNATIONAL STANDARD ISO11843-4First edition2003-11-01Capability of detection P
7、art 4: Methodology for comparing the minimum detectable value with a given value Capacit de dtection Partie 4: Mthodologie de comparaison de la valeur minimale dtectable avec une valeur donne SANS 11843-4:2009This s tandard may only be used and printed by approved subscription and freemailing client
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12、elow 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 Switzerland ii ISO 2003 All rights reservedSANS 11843-4:2009This s tandard may only be us
13、ed and printed by approved subscription and freemailing clients of the SABS .ISO 11843-4:2003(E) ISO 2003 All rights reserved iiiForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing Interna
14、tional Standards is normally carried 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
15、ISO, also take part in the work. 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
16、committees is to prepare International 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 t
17、he possibility that some of the 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, Measureme
18、nt methods and results. ISO 11843 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 calibrati
19、on data are used Part 4: Methodology for comparing the minimum detectable value with a given value SANS 11843-4:2009This s tandard may only be used and printed by approved subscription and freemailing clients of the SABS .ISO 11843-4:2003(E) iv ISO 2003 All rights reservedIntroduction An ideal requi
20、rement for the capability of detection with respect to a selected state variable would be that the actual state of every observed system can be classified with certainty as either equal to or different from its basic state. However, due to systematic and random variations, this ideal requirement can
21、not be satisfied for the following reasons. a) In reality all reference states, including the basic state, are never known in absolute terms 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 varia
22、ble. b) In order to prevent erroneous decisions, it is generally recommended to report differences from the basic state only, i.e. data in 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 conseq
23、uence, in those two documents reference states are without justification assumed to be known with respect to the state variable. c) Furthermore, 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
24、 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 detecting that a system, for which the value of the net state variable is equal to the minimum detectable value (xd) is not in the basic state. SANS 11843-4:2009
25、This s tandard may only be used and printed by approved subscription and freemailing clients of the SABS .INTERNATIONAL STANDARD ISO 11843-4:2003(E) ISO 2003 All rights reserved 1Capability of detection Part 4: Methodology for comparing the minimum detectable value with a given value 1 Scope This pa
26、rt 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 value of the net state variable NOTE These assumptions are o
27、ften 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 the net state variable, and the basic experimental design f
28、or 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 is less than a given value. 2 Normative references The fol
29、lowing 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. ISO 3534-1, Statistics Vocabulary and symbols Part 1: Pr
30、obability 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 data Tests for departure from normal distribution ISO 5725
31、-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 materials ISO 11843-1:1997, Capability of detection Part 1
32、: 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) SANS 11843-4:2009This s tandard may only be used and printed by approved subscription and freemailing clients of the SABS .ISO 11843-4:2003(E
33、) 2 ISO 2003 All rights reserved3 Terms and definitions 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 standardi
34、zed. The same complete method shall be used for 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 variabl
35、e (i.e. in analytical chemistry, a sample of the blank material), and a given value, xg, 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 compo
36、sition of the material to be measured in order 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 replicati
37、ons for both reference states specified in 4.2. 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
38、the number of replications used in the assessment 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 me
39、thod; K is the number of replications of measurements 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.
40、NOTE In validation of a method, the capability 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 i
41、ndependent and normally distributed, and the reference and test materials behave in the same way in the measurement system. SANS 11843-4:2009This s tandard may only be used and printed by approved subscription and freemailing clients of the SABS .ISO 11843-4:2003(E) ISO 2003 All rights reserved 35.2
42、 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 (in 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 equ
43、al to zero), the critical value of the response for the test sample (the mean of K measurements) is given by cb1b11yyzJ K=+ + (1) The meanings of the 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 ne
44、t state variable, the critical value of the response is given by cb1b11yyzJ K= + (2) where ycnow is a lower limit. In this situation, the expressions g band gby y in 5.3, 5.4 and Clause 6 are changed to b gand bgy y respectively. 5.3 Probability of detecting a given value of the net state variable I
45、nstead 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 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, xg, of
46、 the net state variable. If this criterion is satisfied, it may be concluded that the minimum detectable value is less than or equal to xg. If the standard deviation of the response for a given value xgof the net state variable is g, the criterion for the power to be greater than or equal to 1 is gi
47、ven by 22gb1b 1 b g11 1 1zzJK J K +W (3) where band gare the expected values under the actual performance conditions for the responses of the basic state and a sample with the net state variable equal to xg. NOTE Criterion (3) follows from the definition of net state variable and Figure 1 of ISO 118
48、43-1:1997. With = , K = J and under the assumption that gW b(it is unusual for the standard deviation to decrease as the net state variable increases), the criterion is simplified to gb122bg2zJ+W (4) 5.4 Confirmation of the criterion for sufficient capability of detection The standard deviations and
49、 expected values of the responses in Criterion (3) are usually unknown and the fulfilment of the criterion has to be confirmed 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. SANS 11843-4:2009This s tandard may only be used and printed by approved subscription and freemailing clients of the SABS .
