1、BRITISH STANDARD BS ISO 11843-3:2003 Capability of detection Part 3: Methodology for determination of the critical value for the response variable when no calibration data are used ICS 03.120.30; 17.020 BS ISO 11843-3:2003 This British Standard was published under the authority of the Standards Poli
2、cy and Strategy Committee on 11 September 2003 BSI 11 September 2003 ISBN 0 580 42609 2 National foreword This British Standard reproduces verbatim ISO 11843-3:2003 and implements it as the UK national standard. The UK participation in its preparation was entrusted to Technical Committee SS/6, Preci
3、sion of test methods, which has the responsibility 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 u
4、nder the section entitled “International 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 a
5、pplication. Compliance with a British Standard 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
6、; monitor related international and European 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 v, a blank page, pages 1 to 9 and a back cover. The BSI copyright notice displayed in this document
7、indicates when the document was last issued. Amendments issued since publication Amd. No. Date Comments Reference number ISO 11843-3:2003(E) OSI 3002INTERNATIONAL STANDARD ISO 11843-3 First edition 2003-04-15 Capability of detection Part 3: Methodology for determination of the critical value for the
8、 response variable when no calibration data are used Capacit de dtection Partie 3: Mthodologie pour dterminer la valeur critique dune variable de rponse lorsque aucun talonnage nest utilis BSISO118433:2003IS-34811 O3:(3002E) DPlcsid Fremia ihTs PDF file mya ctnoian emdebt dedyfepcaes. In ccacnadrow
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13、 av leT. 4 + 10 947 22 1 11 xaF0 947 22 14 + 9 74 E-mial coirypthgis.o gro We bwww.is.o groii ISO 3002 Allr ihgtsser edevrBSISO118433:2003IS-34811 O3:(3002E) I SO 3002 All irhgts seredevr iiiContents Page Foreword iv Introduction v 1 Scope 1 2 Normative references . 1 3 Terms and definitions. 2 4 Ex
14、perimental design . 2 5 Computation of the critical value of the response variable y c . 3 Annex A (normative) Symbols used in this part of ISO 11843 .6 Annex B (informative) Examples. 7 BSISO118433:2003IS-34811 O3:(3002E) iv I SO 3002 All irhgts seredevrForeword ISO (the International Organization
15、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 technical committees. Each member body interested in a subject for which a technical committee has been established has t
16、he 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 with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Interna
17、tional 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 International Standards adopted by the technical committees are circulated to the member bodies for voting. Publicatio
18、n 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 be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights
19、. ISO 11843-3 was prepared by Technical Committee ISO/TC 69, Applications of statistical methods, Subcommittee SC 6, Measurement 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 l
20、inear calibration case Part 3: Methodology for determination of the critical value for the response variable when no calibration data are used Part 4: Methodology for comparing the minimum detectable value with a given value BSISO118433:2003IS-34811 O3:(3002E) I SO 3002 All irhgts seredevr vIntroduc
21、tion 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 can be classified with certainty as either equal to or different from its basic state. However, due to systematic and random variations, this id
22、eal requirement cannot be satisfied because: 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 variab
23、le. 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. Furthermore, the calibration and the pr
24、ocesses of sampling and sample preparation add random variation to the measurement results. In this part of ISO 11843, the symbol is used for the probability of detecting (erroneously) that a system is not in the basic state when it is in the basic state. BSISO118433:2003blank BSISO118433:2003INTENR
25、ATIONAL TSANDADR IS-34811 O3:(3002E)I SO 3002 All irhgts seredevr 1Capability of detection Part 3: Methodology for determination of the critical value for the response variable when no calibration data are used 1 Scope This part of ISO 11843 gives a method of estimating the critical value of the res
26、ponse variable from the mean and standard deviation of repeated measurements of the reference state in certain situations (see 5.1) in which the value of the net state variable is zero, for all reasonable and foreseeable purposes. Hence, it can be decided whether values of the response variable in a
27、n actual state (or test sample) are above the range of values attributable to the reference state. General procedures for determination of critical values of the response variable and the net state variable and of the minimum detectable value have been given in ISO 11843-2. Those procedures are appl
28、icable in situations in which there is relevant straight-line calibration and the residual standard deviation of the measured responses is either constant or is a linear function of the net state variable. The procedure given in this part of ISO 11843 for the determination of the critical value of t
29、he response variable only is recommended for situations in which no calibration data are used. The distribution of data is assumed to be normal or near- normal. The procedure given in this part of ISO 11843 is recommended for situations in which it is difficult to obtain a large amount of the actual
30、 states although a large amount of the basic state can be prepared. 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 doc
31、ument (including any amendments) applies. ISO 3534-1, Statistics Vocabulary and symbols Part 1: Probability and general statistical terms ISO 3534-2, Statistics Vocabulary and symbols Part 2: Statistical quality control ISO 3534-3, Statistics Vocabulary and symbols Part 3: Design of experiments ISO
32、5479:1997, Statistical interpretation of 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:
33、1996, Linear calibration using reference materials ISO 11843-1:1997, Capability of detection Part 1: Terms and definitions ISO 11843-2:2000, Capability of detection Part 2: Methodology in the linear calibration case ISO Guide 30, Terms and definitions used in connection with reference materials BSIS
34、O118433:2003IS-34811 O3:(3002E) 2 I SO 3002 All irhgts seredevr3 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 3534 (all parts), ISO Guide 30, ISO 5479, ISO 5725-2, ISO 11095 and ISO 11843-1 apply. 4 Experimental design 4.1 General The measurement me
35、thod is assumed to be standardized and known to have been calibrated for measurements of a similar type, although calibration under the specific conditions being studied and at very low levels of the net state variable has not been undertaken or is not possible. The same complete measurement method
36、shall be used for all replicated measurements of the reference state in which the state variable is zero as well as for actual states (test samples) within the measurement series for which a critical value of the response variable is required. Measurements of actual states shall be randomized among
37、the measurements of the basic state. Negative values of the response variable shall not be discarded or altered if these arise. For example, negative values shall not be replaced by zeros. 4.2 Choice of the reference state in which the value of the net state variable is zero One of the assumptions i
38、n the procedure described in this part of ISO 11843 is that the value of the net state variable is zero in the reference state chosen. The certainty that can be expected in relation to such an assertion is discussed in ISO 11843-2:2000, Subclause 4.1: in reality, reference states are not known in ab
39、solute terms of the state variable but only in terms of differences from a (hypothetical) basic state. For this part of ISO 11843, it is sufficient for the reference level to be well below that likely to be measured by the method being used. In cases in which the basic state is represented by a prep
40、aration of a reference material, the composition should be as close as possible to the composition of the material to be measured, i.e. in analytical chemistry the blank matrix material chosen should be very similar in every way to, if not identical with, the samples being examined in that measureme
41、nt series. Influences due to the presence of other substances or elements, or due to the physical state of samples, can be highly significant. In particular, when solutions are being investigated, the use of pure solvents rather than the solvent extracts normally encountered in the measurement metho
42、d is unacceptable. 4.3 Replication 4.3.1 Number of replications, J The response from the method used on the basic state shall be measured for a sufficient number of replicates J of the entire procedure so as to give a good estimate of the mean and of the standard deviation. It is important to have s
43、ufficient data to examine the distribution of data to see whether the response variable is normally, or near-normally, distributed. About 30 measurements should usually ensure that the estimate of the standard deviation will not differ more than 30 % from the true standard deviation with approximate
44、ly 95 % probability. NOTE In some situations, it is not possible to perform the number of measurements outlined above because of constraints on the amount of material available or for other reasons. In such situations, the estimate of the standard deviation obtained is markedly uncertain. When such
45、an estimate s (see s bin 5.2) of a true standard deviation is to be made, conclusions can be drawn as to the range about the interval based on s within which the estimate of can be expected to lie with prespecified probability 1 . This is a statistical problem usually solved (if assumption of normal
46、ity is valid and s is the sample standard deviation) by the use of the chi-squared distribution for the number of results on which the estimate of s was based to give a confidence interval for the value of of BSISO118433:2003IS-34811 O3:(3002E) I SO 3002 All irhgts seredevr 3() () 22 22 1 s|= 0 ) Py
47、 y x u (1) NOTE ac (|= 0 ) Py y x is the probability that ac yy under the condition that x = 0. The definition may be stated as an equality, although the inequality accommodates discrete distributions, such as the Poisson distribution, for which not all values of are possible. If a) y is normally di
48、stributed with standard deviation 0 , b) samples of actual states are as homogeneous as possible, c) the measurements are unbiased, BSISO118433:2003IS-34811 O3:(3002E) 4 I SO 3002 All irhgts seredevrthe critical value of the response variable is given by the following simplified expression of Equati
49、on (1): 10 cb 11= + z yy J K (2) where z 1represents the (1 )-quantile of the standard normal variable; 0is the standard deviation of the net signal (or concentration) under the null hypothesis (true value x = 0); J is the number of replicate determinations of the basic state; b y is the arithmetic mean of those replications; K is the number of determinations to be made o
