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 978-0-626-22659-6 SANS 5725-1:2009Edition 1 and ISO tech. corr.1ISO 5725-1:1994Edition 1 and tech. corr.1SOUTH AFRICAN NATIONAL STANDARD Accuracy (t
4、rueness and precision) of measurement methods and results Part 1: General principles and definitions This national standard is the identical implementation of ISO 5725-1:1994 and ISO technical corrigendum 1, and is adopted with the permission of the International Organization for Standardization. Pu
5、blished by SABS Standards Division 1 Dr Lategan Road Groenkloof Private Bag X191 Pretoria 0001Tel: +27 12 428 7911 Fax: +27 12 344 1568 www.sabs.co.za SABS SANS 5725-1:2009 Edition 1 and ISO tech. corr. 1 ISO 5725-1:1994 Edition 1 and tech. corr. 1 Table of changes Change No. Date Scope ISO tech. co
6、rr. 1 1998 Corrected to replace table 2 with a new table. National foreword This South African standard was approved by National Committee SABS TC 169, Applications of statistical methods, in accordance with procedures of the SABS Standards Division, in compliance with annex 3 of the WTO/TBT agreeme
7、nt. This SANS document was published in August 2009. ICS 03.120.30; 17.020 Ref. No. ISO 5725-1:1994/Cor.1:1998(E)Descriptors: measurement, tests, test results, accuracy, reproducibility, statistical analysis, definitions, generalities. ISO 1998Printed in SwitzerlandAINTERNATIONAL STANDARD ISO 5725-1
8、:1994TECHNICAL CORRIGENDUM 1Published 1998-02-15INTERNATIONAL ORGANIZATION FOR STANDARDIZATION ORGANISATION INTERNATIONALE DE NORMALISATIONAccuracy (trueness and precision) of measurementmethods and results Part 1:General principles and definitionsTECHNICAL CORRIGENDUM 1Exactitude (justesse et fidli
9、t) des rsultats et mthodes de mesure Part 1: Principes gnraux et dfinitionsRECTIFICATIF TECHNIQUE 1Technical Corrigendum 1 to International Standard ISO 5725-1:1994 was prepared by Technical CommitteeISO/TC 69, Applications of statistical methods, Subcommittee SC 6, Measurement methods and results.P
10、age 10, table 2Replace table 2 with the following table (taken from table 1 of ISO 5725-4:1994):SANS 5725-1:2009This s tandard may only be used and printed by approved subscription and freemailing clients of the SABS .ISO 5725-1:1994/Cor.1:1998(E)ISO2Table 2 Values of A, the uncertainty of an estima
11、te of the bias of the measurement methodNo. oflabora-toriesValue of Ag = 1 g = 2 g = 5pn = 2 n = 3 n = 4 n = 2 n = 3 n = 4 n = 2 n = 3 n = 45 0,62 0,51 0,44 0,82 0,80 0,79 0,87 0,86 0,8610 0,44 0,36 0,31 0,58 0,57 0,56 0,61 0,61 0,6115 0,36 0,29 0,25 0,47 0,46 0,46 0,50 0,50 0,5020 0,31 0,25 0,22 0,
12、41 0,40 0,40 0,43 0,43 0,4325 0,28 0,23 0,20 0,37 0,36 0,35 0,39 0,39 0,3930 0,25 0,21 0,18 0,33 0,33 0,32 0,35 0,35 0,3535 0,23 0,19 0,17 0,31 0,30 0,30 0,33 0,33 0,3340 0,22 0,18 0,15 0,29 0,28 0,28 0,31 0,31 0,31SANS 5725-1:2009This s tandard may only be used and printed by approved subscription
13、and freemailing clients of the SABS .INTERNATIONAL STANDARD IS0 5725-l First edition 1994-I 2-15 Accuracy (trueness and precision) of measurement methods and results - Part 1: General principles and definitions Exactitude (justesse et fidblit6) des r the factors that influence the outcome of a measu
14、rement cannot all be completely controlled. In the practical interpretation of measurement data, this vari- ability has to be taken into account. For instance, the difference between a test result and some specified value may be within the scope of un- avoidable random errors, in which case a real d
15、eviation from such a specified value has not been established. Similarly, comparing test results from two batches of material will not indicate a fundamental quality dif- ference if the difference between them can be attributed to the inherent variation in the measurement procedure. 0.3 Many differe
16、nt factors (apart from variations between supposedly identical specimens) may contribute to the variability of results from a measurement method, including: a) the operator; b) c) d e) the equipment used; the calibration of the equipment; the environment (temperature, humidity, air pollution, etc.);
17、 the time elapsed between measurements. The variability between measurements performed by different operators and/or with different equipment will usually be greater than the variability between measurements carried out within a short interval of time by a single operator using the same equipment. 0
18、.4 The general term for variability between repeated measurements is precision. Two conditions of precision, termed repeatability and reproduc- ibility conditions, have been found necessary and, for many practical cases, useful for describing the variability of a measurement method. Un- der repeatab
19、ility conditions, factors a) to e) listed above are considered SANS 5725-1:2009This s tandard may only be used and printed by approved subscription and freemailing clients of the SABS .IS0 5725=1:1994(E constants and do no ibility conditions the contribute to the variability, while under reproduc- v
20、ary and do contribute to the variability of the test results. Thus repeatability and reproducibility are the two extremes of precision, the first describing the minimum and the second the maximum variability in results. Other intermediate conditions between these two extreme conditions of precision
21、are also conceivable, when one or more of factors a) to e) are allowed to vary, and are used in certain specified circumstances. Precision is normally expressed in terms of standard devi- ations. 0 IS0 0.5 The “trueness” of a measurement method is of interest when it is possible to conceive of a tru
22、e value for the property being measured. Al- though, for some measurement methods, the true value cannot be known exactly, it may be possible to have an accepted reference value for the property being measured; for example, if suitable reference materials are available, or if the accepted reference
23、value can be established by refer- ence to another measurement method or by preparation of a known sample. The trueness of the measurement method can be investigated by comparing the accepted reference value with the level of the results given by the measurement method. Trueness is normally expresse
24、d in terms of bias. Bias can arise, for example, in chemical analysis if the measurement method fails to extract all of an element, or if the presence of one element interferes with the determination of another. 0.6 The general term accuracy is used in IS0 5725 to refer to both trueness and precisio
25、n. The term accuracy was at one time used to cover only the one component now named trueness, but it became clear that to many persons it should imply the total displacement of a result from a reference value, due to random as well as systematic effects. The term bias has been in use for statistical
26、 matters for a very long time, but because it caused certain philosophical objections among members of some professions (such as medical and legal practitioners), the positive aspect has been emphasized by the invention of the term trueness. vi SANS 5725-1:2009This s tandard may only be used and pri
27、nted by approved subscription and freemailing clients of the SABS .INTERNATIONAL STANDARD Q ISO IS0 5725=1:1994(E) Accuracy (trueness and precision) of measurement methods and results - Part 1: General principles and definitions 1 Scope 1.1 The purpose of IS0 5725 is as follows: a) to outline the ge
28、neral principles to be understood when assessing accuracy (trueness and precision) of measurement methods and results, and in ap- plications, and to establish practical estimations of the various measures by experiment (IS0 5725-I) I b) to provide a basic method for estimating the two extreme measur
29、es of the precision of measure- ment methods by experiment (IS0 5725-2); c) to provide a procedure for obtaining intermediate measures of precision, giving the circumstances in which they apply and methods for estimating them (IS0 5725-3); d) to provide basic methods for the determination of the tru
30、eness of a measurement method (IS0 5725-4); e) to provide some alternatives to the basic meth- ods, given in IS0 5725-2 and IS0 5725-4, for de- termining the precisior measurement methods fo cumstances (IS0 5725-5); and trueness of * use under certain cir- f) to present some practica I applications
31、of these measures of trueness and precision (IS0 5725-6). I.2 This part of IS0 5725 is concerned exclusively with measurement methods which yield measure- ments on a continuous scale and give a single value as the test result, although this single value may be the outcome of a calculation from a set
32、 of observa- tions. It defines values which describe, in quantitative terms, the ability of a measurement method to give a correct result (trueness) or to replicate a given result (precision). Thus there is an implication that exactly the same thing is being measured, in exactly the same way, and th
33、at the measurement process is un- der control. This part of IS0 5725 may be applied to a very wide range of materials, including liquids, powders and solid objects, manufactured or naturally occurring, provided that due consideration is given to any heterogeneity of the material. 2 Normative referen
34、ces The following standards contain provisions which, through reference in this text, constitute provisions of this part of IS0 5725. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this part of IS0 5725 are enc
35、ouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and IS0 maintain registers of currently valid International Standards. SANS 5725-1:2009This s tandard may only be used and printed by approved subscription and freemailing cli
36、ents of the SABS .IS0 5725-l :I 994(E) 0 IS0 IS0 3534-l :I 993, Statistics - Vocabulary and sym- bols - Part I: Probability and general statistical terms. 3.5 accepted reference value: A value that serves as an agreed-upon reference for comparison, and which is derived as: IS0 5725-2: 1994, Accuracy
37、 (trueness and precision) of measurement methods and results - Part 2: Basic method for the determination of repeatability and re- producibility of a standard measurement method. a) a theoretical or e scientific principles; stablished value, on b) an assigned or certified value, based on exper- imen
38、tal work of some national or international or- IS0 5725-3: 1994, Accuracy (trueness and precision) of measurement methods and results - Part 3: Intermediate measures of the precision of a standard measurement method. ganization; c) a consensus or certified value, based on collabor- ative experimenta
39、l work under the auspices of a scientific or engineering group; IS0 5725-4: 1994, Accuracy (trueness and precision) of measurement methods and results - Part 4: Basic methods for the determination of the trueness of a standard measurement method. d) when a), b) and c) are not available, the expec- t
40、ation of the (measurable) quantity, i.e. the mean of a specified population of measurements. ISO 3534-I 36 . a tes accuracy: The closeness of agreement between t result and the accepted reference value. 3 Definitions For the purposes of IS0 5725, the following defi- nitions apply. NOTE 2 The term ac
41、curacy, when applied to a set of test results, involves a combination of random components and a common systematic error or bias component. Some definitions are taken from IS0 3534-l. ISO 3534-I The symbols used in IS0 5725 are given in annex A. 3.7 trueness: The closeness of agreement between the a
42、verage value obtained from a large series of test results and an accepted reference value. 3.1 observed value: The value of a characteristic obtained as the result of a single observation. ISO 3534-I NOTES 3.2 test result: The value of a characteristic ob- tained by carrying out a specified test met
43、hod. 3 The measure of trueness is usually expressed in terms of bias. 4 Trueness has been referred to as “accuracy of the mean”. This usage is not recommen ded. NOTE 1 The test method should specify that one or a number of individual observations be made, and their aver- age or another appropriate f
44、unction (such as the median or the standard deviation) be reported as the test result. It may also require standard corrections to be applied, such as correction of gas volumes to standard temperature and pressure. Thus a test result can be a result calculated from several observed values. In the si
45、mple case, the test result is the observed value itself. ISO 3534-I 3.8 bias: The difference between the expectation of the test results and an accepted reference value. NOTE 5 Bias is the total systematic error as contrasted to random error. There may be one or more systematic error components cont
46、ributing to the bias. A larger systematic difference from the accepted reference value is reflected by a larger bias value. ISO 3534-I 3.3 level of the test in a precision experiment: The general average of the test results from all lab- oratories for one particular material or specimen tested. ISO
47、3534-l-J 3.9 laboratory bias: The difference between the expectation of the test results from a particular lab- oratory and an accepted reference value. 34 . cell in a precision experiment: The test at a single level obtained by one laboratory. 2 SANS 5725-1:2009This s tandard may only be used and p
48、rinted by approved subscription and freemailing clients of the SABS .Q IS0 IS0 5725=1:1994(E) 3.10 bias of the measurement method: The dif- ference between the expectation of test results ob- tained from all laboratories using that method and an accepted reference value. NOTE 6 One example of this i
49、n operation would be where a method purporting to measure the sulfur content of a compound consistently fails to extract all the sulfur, giving a negative bias to the measurement method. The bias of the measurement method is measured by the dis- placement of the average of results from a large number of different laboratories all using the same method. The bias of a measurement method may be different at different levels. 3.11 laboratory component of bias: T between the laboratory bias and the measurement method. he dif bia
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