1、Designation: D 6631 05Standard Guide forCommittee D01 for Conducting an Interlaboratory Study forthe Purpose of Determining the Precision of a Test Method1This standard is issued under the fixed designation D 6631; the number immediately following the designation indicates the year oforiginal adopti
2、on or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide covers a simplified statistical procedure forplanning and cond
3、ucting interlaboratory evaluations of testmethods.2. Referenced Documents2.1 ASTM Standards:2E 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 456 Terminology for Relating to Quality and StatisticsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precis
4、ion of a Test MethodE 1345 Practice for Reducing the Effect of Variability ofColor Measurements by Use of Multiple Measurements3. Significance and Use3.1 The purpose of an interlaboratory evaluation, as definedin this guide, is to determine the variability of results obtainedin different laboratorie
5、s on equivalent equipment using aprescribed test method.3.2 The definitions of statistical terms used in this guide arecontained in Terminology E 456.4. Problem Formulation4.1 The objective of the evaluation should be to clearlydefine the expected precision of the test method. Within thecurrent limi
6、ts of both the software, and the statistical protocolscurrently available, this effectively restricts the use of thisguide to test methods which yield results that are continuous.This generally means a measured quantity, such as pH orbrightness. Results that are discrete (such as counts or pass-fail
7、), or ordered (ranked), present three special problems in thecreation of a meaningful precision statement:4.1.1 The amount of information contained in discrete andordered data is much less than in continuous data, necessitatingthe collection of much more data.4.1.2 The sensitivity (the ability to di
8、scriminate betweensimilar samples) is much less in discrete and ordered data thancontinuous data.4.1.3 Since the precision statement relies on the normaldistribution, and the distributions of discrete and ordered dataare usually decidedly non-normal, the normal precision state-ment is invalid.4.2 Gi
9、ven these concerns with discrete and ordered data, asimple statement of the results obtained in these types ofstudies might be the most useful information for a prospectiveuser of a test method.5. Preliminary5.1 Flow chart the test method.5.2 Survey known sources of information related to the testme
10、thod to establish how results are affected by variations inoperating conditions, atmospheric conditions, differences be-tween operators, etc. Select what appears to be the optimumprocedure.5.3 Provide instructions for the test method and, withoutcomment, observe a laboratory technician perform a tes
11、taccording to these instructions. Revise any parts of the draftcausing difficulty.5.4 If desirable, make a comparative study with other testmethods for measuring the property by using specimens with awide range of values of the property under test (and possiblywith wide ranges in other properties).6
12、. Preparation for Interlaboratory Study6.1 Prepare a clear statement of the type of informationrequired from the interlaboratory evaluation.6.2 Based on the study made in one laboratory (Section 5),prepare a proposed master plan for the interlaboratory evalu-ation. Discuss the plan, in an open meeti
13、ng, if possible, withother participants in the study.6.3 Select the materials to be used in the interlaboratoryevaluations so as to:6.3.1 Cover the applicable range of the property or compo-nent to be measured, and1This guide is under the jurisdiction of ASTM Committee D01 on Paint andRelated Coatin
14、gs, Materials, and Applications and is the direct responsibility ofSubcommittee D01.20 on Quality Assurance and Statistics.Current edition approved July 1, 2005. Published July 2005. Originally approvedin 2001. Last previous edition approved in 2001 as D 6631 01.2For referenced ASTM standards, visit
15、 the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-295
16、9, United States.6.3.2 Represent as many classes of materials as feasible, towhich the test method will be applied.7. Pilot Evaluation7.1 If the test method is new or the procedure for an old testmethod is greatly altered, a pilot study by one laboratoryinvolving a few materials (two or three) may r
17、eveal seriouslymisleading directions in the written procedure. A Box andWhisker Plot (as outlined in Practice E 1345), or a Violin Plot3may help to clarify this evaluation.8. Participating Laboratory Qualification8.1 It is important that the managers of proposed partici-pants in an interlaboratory s
18、tudy be aware of the capability ofthose participants to run the method under study. This is not theresponsibility of the originator of the study, or ASTM. A Boxand Whisker Plot will also be helpful in this qualificationprotocol.9. First Interlaboratory Evaluation9.1 For the first interlaboratory eva
19、luation use at least threematerials to cover the expected range in property values andinclude all of the laboratories that will participate in the maininterlaboratory evaluation. This evaluation will clarify theprocedure, eliminate laboratories that do not comply with theprocedure because of nonstan
20、dard conditions or equipmentand, together with the main study, give some idea of-the timeconstancy of laboratory results.10. Main Interlaboratory Evaluation10.1 VariablesThe major variables that can be included inan interlaboratory evaluation of a test method are: materials,laboratories, apparatus,
21、and replicates, described as follows:(In the event that the minimums for these variables cannot bemet, it is advisable that the recommendation in 4.2 be consid-ered, or that the study be abandoned).10.1.1 MaterialsA minimum of six materials differing inthe property or component to be measured and co
22、vering theuseful scales of the process are needed to evaluate thesensitivity of a test method.10.1.2 LaboratoriesIn the evaluation of a test method, anabsolute minimum of three laboratories or locales must beused, but at least five are strongly recommended.10.1.3 ApparatusIf different types of appar
23、atus (or differ-ent procedures) are to be included in the study, an absoluteminimum of three laboratories is required for each type. Atleast five are needed to obtain a reasonable estimate ofreproducibility. (It must be emphasized that the word “differ-ent” in this section, could apply to multiple m
24、anufacturers, ormodels of equipment.) However, different equipment, usingdifferent techniques or protocols for measurement, for ex-ample, rotational and efflux cup viscometers, must NOT beused in the same study.10.1.4 ReplicatesEach evaluation must at least be run induplicate.10.2 Intralaboratory Pr
25、ecision is usually ascertained byhaving repeats made over the shortest possible time, preferablythe same day. If considered desirable, a completely unbiasedestimate of intralaboratory error can be obtained by use of“blind” repetition. In this procedure two samples of at leastone, and preferably more
26、, of the test materials are distributed asseparate materials. If all the materials are duplicated, the totalamount of work can be kept the same by not repeating the testat another time. However, elimination of the time variablemight alert cooperators to the use of blind repetition which, inany event
27、, is not readily applicable when all the test materialsdiffer markedly in properties.10.3 For analytical test methods, the precision of which isusually very good, two repeats each in duplicate are oftensufficient. However, owing to the much more variable nature ofmeasurements of the physical or appl
28、ication test properties, therepeats should be increased, unless it has been decided to usea test method mainly for ranking a series of materials. For mosttest methods of this type, three repeats should be used, but evenwhen the precision is quite poor the suggested maximum isfour. If the intralabora
29、tory variability is high, the number ofreplications should also be increased.10.4 In order to obtain sufficient interlaboratory degrees offreedom so that the estimated interlaboratory precision will notappear poorer than it really is, the number of laboratories mustincrease as the number of test mat
30、erials decreases.Materials Available Labs Needed544536NOTE 1In contrast to 10.1.1, regarding testing for sensitivity, thistable is designed to show the testing required to evaluate precision.10.5 Instructions to ParticipantUse the master planagreed upon by the evaluation group after careful discussi
31、on.This plan should include instructions on the following:10.5.1 Care of round-robin specimens and what to do incase of loss of specimens or results (missing results can beignored only if a sufficient number of participating laboratoriesand materials are included),10.5.2 Adjustment and calibration o
32、f the test apparatus,10.5.3 Order of testing the specimens,10.5.4 Recording results on the test form,10.5.5 Detailed test procedure, to include:10.5.5.1 Scope,10.5.5.2 Test method,10.5.5.3 Other instructions relevant to use of test method oroperation, as for example, replication and standardization,
33、10.5.5.4 Dates for performance of tests,10.5.5.5 Instructions about personnel,10.5.5.6 Instructions on compilation, calculation, and re-porting,10.5.5.7 Standard report form for results and conditions,10.5.5.8 Instructions on return of reports and, if applicable,materials (including address), and10.
34、5.5.9 Closing date.10.6 Allocation of SpecimensIf appropriate, specimensmay be selected from several locales, but should be coordi-nated from one place. Prepare from each material enough3Hintze, J. L., and Nelson, R. D., “Violin Plots: A Box Plot-Density TraceSynergism”, The American Statistician, M
35、ay 1998, pp. 181-184.D6631052specimens to provide the required test material for the partici-pating laboratories and a sufficient number of additionalspecimens for replacement of lost or spoiled specimens. Labeleach specimen by means of a code symbol and identify thespecimens on a separate key sheet
36、 for future reference.Completely randomize the specimens of a particular materialbefore dividing them into groups to be distributed among thelaboratories. Where necessary, the same specimens may be sentin turn to each participating laboratory.10.7 Results FormSupply each laboratory with resultsforms
37、 to ensure that all results and pertinent information arereported in a uniform manner. In addition to space formeasurement results, the form should provide space for suchinformation as: relative humidity, temperature, instrumenttype, deviations from the specified procedure, unusual obser-vations, an
38、d constructive comments, as required.10.8 Final ReportAfter all participating laboratories re-port their results, and the results are analyzed statistically,according to Practice E 691, or a method that yields equivalentresults, a research report shall be generated giving suchinformation as: the raw
39、 data, the observations from 10.7, andthe statistical analysis results. In addition, a precision statement(and if appropriate, a bias statement), shall be created, accord-ing to Practice E 177.11. Keywords11.1 bias; interlaboratory study; precisionASTM International takes no position respecting the
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42、quarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This sta
43、ndard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D6631053
