SANS 5725-3-2009 Accuracy (trueness and precision) of measurement methods and results Part 3 Intermediate measures of the precision of a standard measurement method《测量方法及结果的精度(真实度及.pdf

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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 978-0-626-22661-9 SANS 5725-3:2009Edition 1 and ISO tech. corr. 1ISO 5725-3:1994Edition 1 and tech. corr. 1SOUTH AFRICAN NATIONAL STANDARD Accuracy

4、(trueness and precision) of measurement methods and results Part 3: Intermediate measures of the precision of a standard measurement method This national standard is the identical implementation of ISO 5725-3:1994 and ISO technical corrigendum 1, and is adopted with the permission of the Internation

5、al Organization for Standardization. Published 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 5725-3:2009 Edition 1 and ISO tech. corr. 1 ISO 5725-3:1994 Edition 1 and tech. corr. 1 Table of cha

6、nges Change No. Date Scope ISO tech. corr. 1 2001 Corrected to change formulas for the ANOVA table for a four-factor fully-nested experiment and the ANOVA table for a four-factor staggered-nested experiment. National foreword This South African standard was approved by National Committee SABS TC 169

7、, Applications of statistical 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 August 2009. ICS 03.120.30 Ref. No. ISO 5725-3:1994/Cor.1:2001(E) ISO 2001 All rights reserved Printed in Swit

8、zerland INTERNATIONAL STANDARD ISO 5725-3:1994 TECHNICAL CORRIGENDUM 1 Published 2001-10-15 INTERNATIONAL ORGANIZATION FOR STANDARDIZATION ORGANISATION INTERNATIONALE DE NORMALISATIONAccuracy (trueness and precision) of measurement methods and results Part 3: Intermediate measures of the precision o

9、f a standard measurement method TECHNICAL CORRIGENDUM 1 Exactitude (justesse et fidlit) des rsultats et mthodes de mesure Partie 3: Mesures intermdiaires de la fidlit dune mthode de mesure normalise RECTIFICATIF TECHNIQUE 1 Technical Corrigendum 1 to International Standard ISO 5725-3:1994 was prepar

10、ed by Technical Committee ISO/TC 69, Applications of statistical methods, Subcommittee SC 6, Measurement methods and results. Page 14, 4th and 5th lines below Table B.2 Replace ()2(1)1“MS2MS1”4s = with ()2(1)1“MS1MS2”.4s = Replace ()2(2)1“MS1MSe”2s = with ()2(2)1“MS2MSe”.2s = Page 17, Table C.2, col

11、umn “Sum of squares” for “Source 0” Replace () ()2 2(2)“4 4 ”iiypywith () ()2 2(3)“4 4 ”.iiypySANS 5725-3:2009This s tandard may only be used and printed by approved subscription and freemailing clients of the SABS .SANS 5725-3:2009This standard may only be used and printed by approved subscription

12、and freemailing clients of the SABS .INTERNATIONAL STANDARD Is0 5725-3 First edition 1994-12-15 Accuracy (trueness and precision) of measurement methods and results - Part 3: Intermediate measures of the precision of a standard measurement method Exactitude (justesse et fide/S) des r b) the equipmen

13、t used; c) the calibration of the equipment; e) f 1 the environment (temperature, humidity, air pollution, etc.); the batch of a reagent; the time elapsed between measurements. The variability between measurements performed by different operators and/or with different equipment will usually be great

14、er than the variability between measurements carried out within a short interval of time by a single operator using the same equipment. 0.4 Two conditions of precision, termed repeatability and reproducibility conditions, have been found necessary and, for many practical cases, useful for describing

15、 the variability of a measurement method. Under re- peatability conditions, factors a) to f) in 0.3 are considered constants and do not contribute to the variability, while under reproducibility conditions they vary and do contribute to the variability of the test results. Thus re- peatability and r

16、eproducibility conditions are the two extremes of pre- cision, the first describing the minimum and the second the maximum variability in results. Intermediate conditions between these two extreme conditions of precision are also conceivable, when one or more of factors V SANS 5725-3:2009This s tand

17、ard may only be used and printed by approved subscription and freemailing clients of the SABS .IS0 57253: 1994(E) 0 IS0 a) to f) are allowed to vary, and are used in certain specified circum- stances. Precision is normally expressed in terms of standard deviations. 0.5 This part of IS0 5725 focuses

18、on intermediate precision measures of a measurement method. Such measures are called intermediate as their magnitude lies between the two extreme measures of the precision of a measurement method: repeatability and reproducibility standard de- viations. To illustrate the need for such intermediate p

19、recision measures, consider the operation of a present-day laboratory connected with a production plant involving, for example, a three-shift working system where measurements are made by different operators on different equipment. Operators and equipment are then some of the factors that contribute

20、 to the variability in the test results. These factors need to be taken into ac- count when assessing the precision of the measurement method. 0.6 The intermediate precision measures defined in this part of IS0 5725 are primarily useful when their estimation is part of a procedure that aims at devel

21、oping, standardizing, or controlling a measurement method within a laboratory. These measures can also be estimated in a specially designed interlaboratory study, but their interpretation and appli- cation then requires caution for reasons explained in 1.3 and 9.1. 0.7 The four factors most likely t

22、o influence the measurement method are the following. precision of a a) Time: whether the time interval between successive measurements is short or long. b) d Calibration: whether the same equipment is or is not recalibrated between successive groups of measurements. Operator: whether the same or di

23、fferent operators carry out the suc- cessive measurements. d) Equipment: whether the same or different equipment (or the same or different batches of reagents) is used in the measurements. 0.8 It is, therefore, advantageous to introduce the following M-factor- different intermediate precision condit

24、ions (M = 1, 2, 3 or 4) to take ac- count of changes in measurement conditions (time, calibration, operator and equipment) within a laboratory. a) M = 1: only one of the four factors is different; b) M = 2: two of the four factors are different; c) M = 3: three of the four factors are different; d)

25、M = 4: all four factors are different. Different intermediate precision conditions lead to different intermediate precision standard deviations denoted by sI( ), where the specific con- ditions are listed within the parentheses. For example, sIcro) is the inter- VI SANS 5725-3:2009This s tandard may

26、 only be used and printed by approved subscription and freemailing clients of the SABS .0 IS0 IS0 5725-3: 1994(E) mediate precision standard deviation with different times (T) and operators (0). 0.9 For measurements under intermediate precision conditions, one or more of the factors listed in 0.7 is

27、 or are different. Under repeatability conditions, those factors are assumed to be constant. The standard deviation of test results obtained under repeatability con- ditions is generally less than that obtained under the conditions for inter- mediate precision conditions. Generally in chemical analy

28、sis, the standard deviation under intermediate precision conditions may be two or three times as large as that under repeatability conditions. It should not, of course, exceed the reproducibility standard deviation. As an example, in the determination of copper in copper ore, a collaborative experim

29、ent among 35 laboratories revealed that the standard deviation under one-factor-different intermediate precision conditions (op- erator and equipment the same but time different) was I,5 times larger than that under repeatability conditions, both for the electrolytic gravimetry and Na,S,O, titration

30、 methods. Vii SANS 5725-3:2009This s tandard may only be used and printed by approved subscription and freemailing clients of the SABS .This page intentionally left blank SANS 5725-3:2009This s tandard may only be used and printed by approved subscription and freemailing clients of the SABS .INTERNA

31、TIONAL STANDARD 0 IS0 IS0 5725-3: 1994(E) Accuracy (trueness and precision) of measurement methods and results - Part 3: Intermediate measures of the precision of a standard measurement method 1 Scope 1.1 This part of IS0 5725 specifies four intermedi- ate precision measures due to changes in observ

32、ation conditions (time, calibration, operator and equipment) within a laboratory. These intermediate measures can be established by an experiment within a specific laboratory or by an interlaboratory experiment. Furthermore, this part of IS0 5725 a) b) d d) discusses the implications of the definiti

33、ons of in- termediate precision measures; presents guidance on the interpretation and appli- cation of the estimates of intermediate precision measures in practical situations; does not provide any measure of the errors in estimating intermediate precision measures; does not concern itself with dete

34、rmining the trueness of the measurement method itself, but does discuss the connections between trueness and measurement conditions. 1.2 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

35、, although the single value may be the outcome of a calculation from a set of obser- vations. 1.3 The essence of the determination of these in- termediate precision measures is that they measure the ability of the measurement method to repeat test results under the defined conditions. 1.4 The statis

36、tical methods developed in this part of IS0 5725 rely on the premise that one can pool information from “similar” measurement conditions to obtain more accurate information on the inter- mediate precision measures. This premise is a powerful one as long as what is claimed as “similar” is indeed “sim

37、ilar”. But it is very difficult for this premise to hold when intermediate precision meas- ures are estimated from an interlaboratory study. For example, controlling the effect of “time” or of “oper- ator” across laboratories in such a way that they are “similar”, so that pooling information from di

38、fferent laboratories makes sense, is very difficult. Thus, using results from interlaboratory studies on intermediate precision measures requires caution. Within- laboratory studies also rely on this premise, but in such studies it is more likely to be realistic, because the control and knowledge of

39、 the actual effect of a factor is then more within reach of the analyst. 1.5 There exist other techniques besides the ones described in this part of IS0 5725 to estimate and to verify intermediate precision measures within a lab- 1 SANS 5725-3:2009This s tandard may only be used and printed by appro

40、ved subscription and freemailing clients of the SABS .IS0 57253: 1994(E) 0 IS0 oratory, for example, control charts (see IS0 5725-6). This part of IS0 5725 does not claim to describe the only approach to the estimation of intermediate pre- cision measures within a specific laboratory. NOTE 1 This pa

41、rt of IS0 5725 refers to designs of ex- periments such as nested designs. Some basic information is given in annexes B and C. Other references in this area are given in annex E. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provis

42、ions 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 encouraged to investigate the possibility of applying the most recent editions of the standards indicated

43、below. Members of IEC and IS0 maintain registers of currently valid International Standards. IS0 3534-l :I 993, Statistics - Vocabulary and sym- bols - Part 1: Probability and general statistical terms. IS0 5725-l : 1994, Accuracy (trueness and precision) of measurement methods and results - Part 1:

44、 General principles and definitions. IS0 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. IS0 Guide 33:1989, Uses of certified reference ma- terials.

45、IS0 Guide 35:1989, Certification of reference ma- terials - General and statistical principles. 3 Definitions For the purposes of this part of IS0 5725, the defi- nitions given in IS0 3534-l and IS0 5725-l apply. The symbols used in IS0 5725 are given in annex A. 4 General requirement In order that

46、the measurements are made in the same way, the measurement method shall have been standardized. All measurements forming part of an experiment within a specific laboratory or of an inter- laboratory experiment shall be carried out according to that standard. 5 Important factors 5.1 Four factors (tim

47、e, calibration, operator and equipment) in the measurement conditions within a laboratory are considered to make the main contri- butions to the variability of measurements (see table I). 52 “Measurements made at the same time” in- clude those conducted in as short a time as feasible in order to min

48、imize changes in conditions, such as environmental conditions, which cannot always be guaranteed constant. ” Measurements made at differ- ent times”, that is those carried out at long intervals of time, may include effects due to changes in en- vironmental conditions. Table 1 - Four important factor

49、s and their states Factor Time Calibration Operator Equipment Measurement conditions within a laboratory State 1 (same) Measurements made at the same time No calibration between measure- ments Same operator Same equipment without recali- bration State 2 (different) Measurements made at different times Calibration carried out between measurements Different operators Different equipment SANS 5725-3:2009This s tandard may only be used and printed by approved subscription and freemailing clients of the SABS .0 IS0 IS0