1、Designation: C 802 96 (Reapproved 2008)1Standard Practice forConducting an Interlaboratory Test Program to Determinethe Precision of Test Methods for Construction Materials1This standard is issued under the fixed designation C 802; the number immediately following the designation indicates the year
2、oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTEA units statement was added editorially as paragraph 1.2 in Dece
3、mber 2008.1. Scope1.1 This practice describes techniques for planning, con-ducting, and analyzing the results of an interlaboratory study ofa test method. It is designed to be used in conjunction withPractice C 670. Thus, the procedures recommended in thispractice have the limited purpose of providi
4、ng reliable infor-mation on which precision statements of the type described inPractice C 670 can be based. It is not appropriate for use inprograms whose purpose is to develop a test method or toassess the relative merits of two or more test methods.1.2 The values stated in inch-pound units are to
5、be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.2. Referenced Documents2.1 ASTM Standards:2C 109/C 109M Test Method for Compressive Strength ofHydraulic Cement Mortars (Using 2-in. o
6、r 50-mm CubeSpecimens)C 136 Test Method for Sieve Analysis of Fine and CoarseAggregatesC 670 Practice for Preparing Precision and Bias Statementsfor Test Methods for Construction MaterialsC 1067 Practice for ConductingARuggedness or ScreeningProgram for Test Methods for Construction MaterialsE 105 P
7、ractice for Probability Sampling Of MaterialsE 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 178 Practice for Dealing With Outlying Observations3. Significance and Use3.1 Certain criteria need to be met before undertaking aninterlaboratory study to determine the precision
8、 of a testmethod. It is not necessary that all of the following conditionsdescribed be completely fulfilled in every case; however, ifsome conditions are not met or are met incompletely, theprogram will become more complicated and require more workand expense, or may result in impaired information.
9、Therecommendations outlined in this section are intended toensure that the test method is free of technical difficulties to thegreatest extent possible before an expensive and time-consuming interlaboratory study is undertaken.3.1.1 The first requirement is the existence of a valid andwell-written t
10、est method that has been developed in onecompetent laboratory (or by cooperative work in a smallnumber of laboratories), and has been subjected to a screeningprocedure, or to ruggedness testing as described in PracticeC 1067. As a result of the screening procedure and someexperience with the test me
11、thod in the sponsoring laboratoryand one or two others, a written version of the test method hasbeen developed (but not necessarily published as a standardmethod) that describes the test procedure in terms that caneasily be followed in any properly equipped laboratory. Con-ditions that affect the te
12、st results should be identified and theproper degree of control of those conditions should be specifiedin the description of the test procedure (see Note 1).NOTE 1The desired degree of control of conditions that affect testresults may not always be practically achievable, and tolerances in the testm
13、ethod should recognize this fact. Variations in test results due tovariations in such conditions contribute to the total variation whichdetermines the precision of the test method. If the resulting variation is sogreat that uncertainties in average values obtained by the test method areunacceptably
14、high, then the test method itself is at fault, and efforts should1This practice is under the jurisdiction of ASTM Committee C09 on Concreteand ConcreteAggregates .This practice was developed jointly byASTM CommitteeC01, C09, D04, and D18, and is endorsed by all four committees.Current edition approv
15、ed Dec. 1, 2008. Published February 2009. Originallyapproved in 1974. Last previous edition approved in 2002 as C 802 96(2002).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information
16、, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.be made to improve it or to replace it by a better one. An expensive andtime-consuming interlaboratory study should not
17、 be undertaken on such atest method.3.1.2 Any apparatus required for performing the test shouldbe appropriately designed and available at reasonable cost.3.1.3 Personnel in participating laboratories should haveenough experience with the test method so that they arecompetent to run the test. The imp
18、ortance of this requirementwill vary with the complexity of the method and the degree towhich it departs from familiar procedures.3.1.4 Preliminary knowledge should exist about howchanges in materials and conditions affect the test results.There should be a reasonable degree of certainty that thewit
19、hin-laboratory variances are the same in different laborato-ries, and that troublesome interactions do not exist. Theseconditions are investigated in the analysis of the data of aninterlaboratory study, and are discussed further in 8.2.2, 8.2.3,and Appendix X1.3.1.5 Facilities and procedures for pro
20、curement, prepara-tion, and distribution of samples must be available and shouldbe as simple and free of difficulties as practicable.3.1.6 Selection of samples must be done by a randomizationprocess, and one person who is familiar with randomizationprocedures should be responsible for seeing that th
21、e procedureis carried out. Refer to Recommended Practice E 105.3.1.7 Adequate numbers of participating laboratories, op-erators, and materials must be available. Requirements in theseareas are specified in Sections 4 and 5.3.1.8 The entire interlaboratory test program should bedeveloped from the beg
22、inning with the help and advice ofpersons familiar with statistical procedures and with thematerials involved (see Note 2). The same persons who designthe experiment should also carry out, or at least have controlover, the process of analysis of the data.NOTE 2It may not always be possible to obtain
23、 people who arefamiliar with the materials involved who have a sufficient knowledge ofthe proper statistical techniques and their proper use. In this case, thecommittee should obtain the services of a competent statistician who hasexperience in practical work with data from materials testing, and pr
24、ovidehim with an opportunity for learning something about the particularmaterials and test method involved. Planners of an interlaboratory studyshould also be warned to avoid the pitfall of assuming that the use of alarge computer necessarily results in special expertise in the handling ofdata or th
25、e interpretation of results.3.2 It is important to bear in mind that estimates of theprecision of a test method are always based on a particular setof data obtained at a particular time and they need to be keptup-to-date.As materials, apparatus, and conditions change, andoperators change or gain mor
26、e experience, the characteristicprecision of the results obtained may change, especially if thetest method is new. In some cases, it may even be desirable toconduct more tests at a later date (though not necessarily arepetition of the complete interlaboratory study) in order toprovide a check on est
27、imates previously obtained and eitherverify them or introduce revisions.4. Laboratories4.1 The problem of obtaining competent participating labo-ratories for an interlaboratory study is often one of the mostdifficult ones connected with the process. The number oflaboratories available is seldom as e
28、xtensive as one would like,and if the test method is new, complicated, or expensive andtime-consuming to run, the problem is further complicated.The problem usually becomes one of finding and obtaining thecooperation of enough qualified laboratories to obtain mean-ingful estimates of precision, rath
29、er than that of selectionamong a group of available laboratories. If there is greatdifficulty in obtaining a sufficient number of competent andwilling laboratories, then the possibility exists that the testmethod should not be subjected to a formal interlaboratorystudy.4.2 For the purposes of progra
30、ms using this recommendedpractice, it is recommended that at least ten participatinglaboratories be included (1, 2).3In cases where it is impossibleto obtain ten laboratories, the effect of an increased numbermay be obtained by repeating the program with the same groupof laboratories six months late
31、r. Usually, results obtained fromthe same laboratory after a time lapse of approximately sixmonths display most of the characteristics of results from adifferent laboratory, especially if a different operator andapparatus can be used. If this procedure is followed, it isnecessary to be sure that the
32、 same materials are used, and thattheir characteristics have not changed in the interim.4.3 In general, it is recommended that any laboratory that isconsidered qualified to run the test in routine testing situationsshould be permitted and encouraged to participate. “Qualified”implies proper laborato
33、ry facilities and testing equipment,competent operators familiar with the test method, a reputationfor reliable testing work, and sufficient time and interest to doa good job. It does not mean, however, that only a select groupof laboratories that are considered to be those best qualified forthe int
34、erlaboratory study should be picked. Precision estimatesfor inclusion in a test method must be obtained under condi-tions and through the efforts of laboratories and personnel thatare representative of the situations in which the test methodwill be used in practice (3). If a laboratory has all the o
35、therrequirements, but its personnel has had insufficient experiencewith the method, the operators in that laboratory should begiven an opportunity to familiarize themselves with the methodand to practice its application before the interlaboratory studystarts.5. Materials5.1 The number and type of ma
36、terials to be included in aninterlaboratory study will depend on the following:5.1.1 The range of the values of the property being mea-sured on a given material and how the precision varies overthat range,5.1.2 The number of different materials to which the testmethod is to be applied,5.1.3 The diff
37、iculty and expense involved in obtaining,processing, and distributing samples,5.1.4 The difficulty of, length of time required for, andexpense of performing the tests, and3The boldface numbers in parentheses refer to the list of references at the end ofthis practice.C 802 96 (2008)125.1.5 The uncert
38、ainty of prior information on any of thesepoints. For example, if it is already known that the precision isrelatively constant or proportional to the average level over therange of values of interest, a smaller number of materials willbe needed than if it is known that the precision changeserratical
39、ly at different levels. A preliminary pilot or screeningprogram may help to settle some of these questions, and mayoften result in the saving of considerable time and expense inthe full interlaboratory study (4).5.2 In general, a minimum of three materials should beconsidered acceptable.6. Estimates
40、 of Precision6.1 In accordance with Recommended Practice C 670, theprocedure described in this practice is designed to provide twobasic estimates of the precision of a test method: (a) single-operator precision, and (b) multilaboratory precision. If otherestimates of precision are desired, other ref
41、erences should beconsulted (see Practice E 177) (5).6.2 Single-operator precision provides an estimate of thedifference that may be expected between duplicate measure-ments made on the same material in the same laboratory by thesame operator using the same apparatus within a time span ofa few days.6
42、.3 Multilaboratory precision provides an estimate of thedifference that may be expected between measurements madeon the same material in two different laboratories.7. Collection of Data7.1 In order to minimize the problems concerned withanalysis of data, a definite form and instructions for obtainin
43、gand recording the data should be developed and distributed toall participating laboratories.7.2 Directions to LaboratoriesThe directions to the labo-ratories should deal mainly with reporting of data. No specialinstructions for performing the tests that differ from thosegiven in the description of
44、the test method should be included.The laboratories should be cautioned to conduct tests andreport results exactly as specified in the test method, with theone exception as noted in 7.2.2.7.2.1 Averaging Test ResultsLaboratories should particu-larly be cautioned against practices such as running a n
45、umberof tests and selecting the “best” ones or reporting the averageof several determinations, except as such averaging is specifiedin the test method. For example, Test Method C 109/C 109Mspecifies three or more test specimens, and requires that thestrength of all acceptable test specimens made fro
46、m the samesample and tested at the same period shall be averaged andreported. In this case, the directions for the interlaboratory testshould specify the number of determinations to be obtained andreported. Whenever a test result is defined, either in the testmethod or in the instructions to laborat
47、ories participating in aninterlaboratory test program, as the average of a particularnumber of determinations, the individual determinationsshould be reported, in addition to the averages. When two ormore measurements are averaged to obtain a test result, thedata from the interlaboratory test progra
48、m may be used todevelop an estimate of the precision of these individualmeasurements. See 3.3.3 of Practice C 670.7.2.2 Rounding of Data:7.2.2.1 Generally, laboratories should be required to reportall figures obtained in making the measurements, rather thanrounding the results before recording them.
49、 In some cases, thismay result in recording of more digits than is customary oreven more than the test method calls for in the section onReporting (see X1.3.1). This is necessary because the variationfrom which information about the precision of the test methodcomes is contained in the least significant digits, which areoften discarded in reporting the results of routine testing (6).For example, Method C 136 calls for reporting of percentagesto the nearest whole number. This is adequate for the usualreporting purposes, but for purposes of determining precision,at least one
