1、Designation: E2480 12 (Reapproved 2017)Standard Practice forConducting an Interlaboratory Study to Determine thePrecision of a Test Method with Multi-Valued Measurands1This standard is issued under the fixed designation E2480; the number immediately following the designation indicates the year ofori
2、ginal 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.1. Scope1.1 This practice describes the techniques for planning,conducting
3、, and analyzing the results of an interlaboratorystudy (ILS) conducted for certain test methods within Com-mittee E12.1.2 This practice does not concern itself with the develop-ment of the test method but rather with the gathering of theinformation needed for the precision and bias statement afterth
4、e completion of development of the test method. The dataobtained in the ILS may indicate, however, that further effort isneeded to improve the test method.1.3 This practice is concerned exclusively with test methodsthat derive a multi-valued measurand, such as, but not limitedto, spectral reflectanc
5、e, transmittance function, tristimulusvalues, or RGB values. Variation in measurements of suchmulti-valued measurands are usually analyzed by reducing thedata to a single-valued parameter, such as color difference, E.1.4 This practice covers methods of dealing with the non-normal distribution of the
6、 variation of sets of color-differences.This is done so that the user may derive valid statistics fromsuch non-normal distributions.1.5 This practice does not cover test methods, even inCommittee E12, whose measurands are single-valued, orwhose variations are known to be normally distributed. Taskgr
7、oups involved with such test methods are referred to PracticeE691 which contains preferable methods of analyzing datawith those properties.1.6 This practice is not intended to establish a method forestimating possible color-difference tolerances.1.7 The values stated in SI units are to be regarded a
8、s thestandard. The values given in parentheses are for informationonly.1.8 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices
9、and deter-mine the applicability of regulatory limitations prior to use.1.9 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Reco
10、m-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE284 Terminology of AppearanceE691 Practice for Conducting an Interlaboratory Study toDet
11、ermine the Precision of a Test MethodE1345 Practice for Reducing the Effect of Variability ofColor Measurement by Use of Multiple Measurements3. Terminology3.1 DefinitionsFor color and appearance terms, see Ter-minology E284.3.2 Definitions of Terms Specific to This Standard:3.2.1 precision and bias
12、, nwhen a test method is appliedto a large number of specimens that are as nearly alike aspossible, the test results obtained nevertheless will not all havethe same values. A measure of the degree of agreement amongthese test results describes the precision of the test method forthat material. This
13、practice is designed only to estimate theprecision of a test method. However, when accepted referencevalues are known for the materials being tested, the test resultdata obtained in accordance with this practice may be used toestimate the bias of the test method. For a discussion of biasestimation,
14、see Practice E177.3.2.2 repeatability and reproducibility, nthe term repeat-ability concerns the variability between independent test results1This practice is under the jurisdiction of ASTM Committee E12 on Color andAppearance and is the direct responsibility of Subcommittee E12.02 on Spectro-photom
15、etry and Colorimetry.Current edition approved Nov. 1, 2017. Published November 2017. Originallyapproved in 2007. Last previous edition approved in 2012 as E2480 12. DOI:10.1520/E2480-12R17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at servic
16、eastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance wit
17、h internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1obtained within a single laboratory in th
18、e shortest practicalperiod of time by a single operator applying the test methodwith a specific set of test apparatus using test specimens takenat random from a single quantity of homogeneous materialobtained, or prepared, for the ILS. The term reproducibilityconcerns the variability between single
19、test results obtained indifferent laboratories, each by a different operator, each ofwhom has applied the test method to specimens taken atrandom from a single quantity of homogeneous materialobtained, or prepared, for the ILS.3.2.2.1 DiscussionThe above single operator and singleapparatus requireme
20、nt, as specified in 3.2.2, means that for aparticular step in the measurement process the same combina-tion of operator and apparatus is used to obtain every test resulton every specimen. Thus, one operator could prepare andmount the specimen, another actuate the measurements, andstill another recor
21、d the value of the result.3.2.2.2 DiscussionThe shortest practical period of timemeans that the test results are obtained in a time not less thannormal testing and not so long as to permit significant changesin material, equipment, calibration, or environment.3.2.2.3 DiscussionThe requirement that t
22、he measurementsbe independent means that a single test determination beginswith the mounting of the specimen on the sample port or in thetransmission compartment, and ends with the removal of thetest specimen from the port or compartment.All measurementsare made with replacement.3.2.2.4 DiscussionTh
23、e requirement for different laborato-ries does not exclude the case where more than one instrumentresides in the same company, laboratory, or room, providedthat each has an independent and separate calibration traceabil-ity path from each other.3.2.3 test method and protocol, nin this practice, the
24、termtest method applies to both the actual measurement process andthe written description of the process, while the term protocolrefers to the written instructions given the participants forconducting the ILS.3.2.4 test specimens, nthe portion of the material beingtested needed for obtaining a singl
25、e test determination is calleda test specimen. A single test specimen may be measured morethan once and the results combined to produce a test result ifthe protocol or test method so specifies.4. Summary of Practice4.1 The procedure presented in this practice consists ofthree steps: planning the int
26、erlaboratory study, guiding thetesting phase of the study, and analyzing the test result data.The analysis includes the calculation of the numerical mea-sures of precision of the test method applying to both within-laboratory repeatability and between-laboratory reproducibil-ity.5. Significance and
27、Use5.1 ASTM regulations require precision statements for alltest methods in terms of repeatability and reproducibility. Thispractice may be used in obtaining the information needed toprepare a precision statement in accordance with Practice E177and the “Blue Book.”PLANNING THE INTERLABORATORY STUDY
28、(ILS)6. ILS Membership6.1 Task GroupEither the task group that developed thetest method or a special task group formed specifically for thepurpose must have overall responsibility for the funding,staffing, design, and decision-making with regard to data in theILS. The task group should decide on the
29、 number oflaboratories, materials, and test results for the ILS. The taskgroup should obtain a statement of willingness to participatefrom each of the participating laboratories. In addition, the taskgroup should obtain, randomize, and distribute the specimensto be tested.6.2 ILS CoordinatorThe task
30、 group must appoint oneindividual to act as overall coordinator of the ILS. This personhas responsibility for distributing the materials and protocols tothe laboratories, and for receiving the test result reports fromthe laboratories.6.3 Statistician:6.3.1 The test method task group should obtain th
31、e assis-tance of a person familiar with the statistical procedures of thispractice and with the materials being tested. When no suchperson is available, the task group should obtain the assistanceof a statistician who has experience in practical work with datafrom materials. Task group members need
32、not be members ofASTM.6.3.2 The calculation of the statistics for each material maybe readily done by persons not having knowledge of statistics,but having basic knowledge of calculating and computers.6.4 Laboratory ILS SupervisorEach participating labora-tory must have an ILS supervisor to oversee
33、the conduct of theILS within the laboratory and to communicate with the ILSCoordinator. This supervisors name should be obtained at thetime that the laboratory states its willingness to participate.7. Basic Design7.1 Keep the design as simple as possible in order to obtainestimates of within- and be
34、tween-laboratory variability that arefree of secondary effects. The basic design is represented by atwo-way classification table, in which the rows represent thelaboratories, and the columns represent the materials, and eachcell (the intersection of a row and a column) contains a testresult made by
35、a particular laboratory on a particular material.8. Test Method8.1 A written version of the test method (but not onenecessarily as yet published as an ASTM standard) must havebeen developed and be distributed with the protocol if other-wise unavailable to the participating laboratories.8.2 The test
36、method should have been subjected to ascreening procedure, in order that some experience with thetest method has been obtained before an ILS is conducted. Testconditions that affect the test results, if any, should be identifiedand a statement of the needed degree of control of theseconditions shoul
37、d be provided. In addition, the test method, orthe protocol, should specify to how many digits of precisioneach test result is to be measured.E2480 12 (2017)28.3 The test method should specify the calibration proce-dure and the frequency of calibration.9. Laboratories9.1 Number of LaboratoriesAn ILS
38、 should be run with nofewer than 8 laboratories. It is recommended that the numberof laboratories be set at 10, and it is desirable that morelaboratories be included if available in order that the ILS isconducted with a reasonable cross-section of competent labo-ratories. Under no circumstances, all
39、owing for attrition, shouldthe final statement of precision of a test method be based onfewer than 6 laboratories when the requisite three materials areemployed.9.1.1 Under some circumstances and with some testmethods, it may be impossible to obtain the necessary sixlaboratories. Under these conditi
40、ons, it is permissible toproceed with the supplementation of additional materials tomake up for the loss of degrees of freedom using the followingschedule of materials and laboratories:Number of LabsRequired MinimumNumber of Materials6354459.2 The ILS should not be restricted to a group of labora-to
41、ries judged to be exceptionally qualified and equipped for theILS. Precision estimates for a test method should be obtainedthrough conditions where laboratories are competent andpersonnel are operating under conditions that will prevail whenthe test method is used in practice.10. Materials10.1 The t
42、erm material means anything with a property thatcan be measured. Different materials having the same propertymay be expected to have different levels of the property,meaning higher or lower levels of the property.10.2 The ILS should include a minimum of three differentmaterials each with a different
43、 levels of the property under test,and to be broadly applicable more than three materials ofdiffering levels should be assessed.10.3 The materials involved in any one ILS should differprimarily in the differing levels of the property being assessedby the test method. When it is known, or suspected,
44、thatdifferent classes of materials will exhibit different levels ofprecision when tested by the test method, consideration shouldbe given to conducting separate interlaboratory studies for eachclass of material.10.4 The ILS should not be restricted to materials that arejudged to be exceptionally qua
45、lified for the ILS. Precisionestimates for a test method should be obtained throughconditions where materials are competent for measurement ofthe property-under-test under conditions that will prevail whenthe test method is used in practice.10.5 If more precise information is required about material
46、sthat are not so competent for measurement of the propertybeing tested, those laboratories directly involved with thematerial in question must conduct interlaboratory studiesspecifically aimed at the material of interest.11. Number of Test Results per Material11.1 The minimum number of test results
47、per laboratory oneach material shall be four. The number may rise to as many asten when test results are apt to vary considerably. The numberof test results in any one ILS will be determined by the TaskGroup, based upon the desired level of tolerance and theanticipated variation of test results from
48、 the test method.12. Protocol12.1 Prepare a written protocol containing instructions forthe participating laboratories to follow. Clearly identify thespecific version of the test method being studied. If the testmethod allows options in apparatus or procedure, clearlyspecify which option has been se
49、lected for conducting the ILS.12.2 Cite the name, address, telephone number, and E-mailaddress of the ILS Coordinator. Urge the participants to call thecoordinator with any questions that may arise as to the conductof the ILS.12.3 Request that the participating laboratory keep a record(or log) of any special events that arise during any phase of thetesting. This record should include any specific aspects of theapparatus, calibration, or procedure that ought to be commu-nicated to the task group to allow them to prepare the finalresearch report on the ILS.12.
