1、Designation: E 2480 07Standard Practice forConducting an Interlaboratory Study to Determine thePrecision of a Test Method with Multi-Valued Measurands1This standard is issued under the fixed designation E 2480; the number immediately following the designation indicates the year oforiginal adoption o
2、r, 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 practice describes the techniques for planning,conducting, and analyzing
3、 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 afterthe completion of
4、 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 reflectance, transmittanc
5、e 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, DE.1.4 This practice covers methods of dealing with the non-normal distribution of the variation of
6、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. Taskgroups involved
7、with such test methods are referred to PracticeE 691 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 as thestandard
8、. 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 and health practices and determine the applica-bil
9、ity of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 284 Terminology of AppearanceE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE 1345 Pract
10、ice for Reducing the Effect of Variability ofColor Measurement by Use of Multiple Measurements3. Terminology3.1 DefinitionsFor color and appearance terms, see Ter-minology E 284.3.2 Definitions of Terms Specific to This Standard:3.2.1 precision and bias, nwhen a test method is appliedto a large numb
11、er 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 practice is designed only to estimate theprecis
12、ion 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, see Practice E 177.3.2.2 repeatability and repr
13、oducibility, nthe term repeat-ability concerns the variability between independent test resultsobtained within a single laboratory in the 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 sin
14、gle quantity of homogeneous materialobtained, or prepared, for the ILS. The term reproducibilityconcerns the variability between single test results obtained indifferent laboratories, each by a different operator, each ofwhom has applied the test method to specimens taken atrandom from a single quan
15、tity of homogeneous materialobtained, or prepared, for the ILS.1This practice is under the jurisdiction of ASTM Committee E12 on Color andAppearance and is the direct responsibility of Subcommittee E12.93 on Precisionand Bias.Current edition approved July 1, 2007. Published August 2007.2For referenc
16、ed ASTM standards, visit 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 Co
17、nshohocken, PA 19428-2959, United States.3.2.2.1 DiscussionThe above single operator and singleapparatus requirement, 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
18、. Thus, one operator could prepare andmount the specimen, another actuate the measurements, andstill another record 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 perm
19、it significant changesin material, equipment, calibration, or environment.3.2.2.3 DiscussionThe requirement that the measure-ments be independent means that a single test determinationbegins with the mounting of the specimen on the sample portor in the transmission compartment, and ends with the rem
20、ovalof the test specimen from the port or compartment. Allmeasurements are made with replacement.3.2.2.4 DiscussionThe 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 independen
21、t and separate calibration traceabil-ity path from each other.3.2.3 test method and protocol, nin this practice, the 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 participa
22、nts forconducting the ILS.3.2.4 test specimens, nthe portion of the material beingtested needed for obtaining a single 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
23、specifies.4. Summary of Practice4.1 The procedure presented in this practice consists ofthree steps: planning the interlaboratory 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
24、 method applying to both within-laboratory repeatability and between-laboratory reproducibil-ity.5. Significance and 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 to
25、prepare a precision statement in accordance with PracticeE 177 and the “Blue Book.”PLANNING THE INTERLABORATORY STUDY (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 fo
26、r the funding,staffing, design, and decision-making with regard to data in theILS. The task group should decide on the number of laborato-ries, materials, and test results for the ILS. The task groupshould obtain a statement of willingness to participate fromeach of the participating laboratories. I
27、n addition, the taskgroup should obtain, randomize, and distribute the specimensto be tested.6.2 ILS CoordinatorThe task 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 r
28、eceiving the test result reports fromthe laboratories.6.3 Statistician:6.3.1 The test method task group should obtain the 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 obtai
29、n the assistanceof a statistician who has experience in practical work with datafrom materials. Task group members need 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 calcu
30、lating and computers.6.4 Laboratory ILS SupervisorEach participating labora-tory must have an ILS supervisor to oversee 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 willingne
31、ss to participate.7. Basic Design7.1 Keep the design as simple as possible in order to obtainestimates of within- and between-laboratory variability that arefree of secondary effects. The basic design is represented by atwo-way classification table, in which the rows represent thelaboratories, and t
32、he columns represent the materials, and eachcell (the intersection of a row and a column) contains a testresult made by 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
33、developed and be distributed with the protocol if other-wise unavailable to the participating laboratories.8.2 The test 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 affec
34、t the test results, if any, should be identifiedand a statement of the needed degree of control of theseconditions should be provided. In addition, the test method, orthe protocol, should specify to how many digits of precisioneach test result is to be measured.8.3 The test method should specify the
35、 calibration proce-dure and the frequency of calibration.9. Laboratories9.1 Number of LaboratoriesAn ILS 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
36、 ILS isconducted with a reasonable cross-section of competent labo-ratories. Under no circumstances, allowing for attrition, shouldE2480072the 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 circumstan
37、ces and with some test meth-ods, it may be impossible to obtain the necessary six labora-tories. Under these conditions, it is permissible to proceed withthe supplementation of additional materials to make up for theloss of degrees of freedom using the following schedule ofmaterials and laboratories
38、:Number of Labs Required MinimumNumber of Materials6354459.2 The ILS should not be restricted to a group of labora-tories judged to be exceptionally qualified and equipped for theILS. Precision estimates for a test method should be obtainedthrough conditions where laboratories are competent andperso
39、nnel are operating under conditions that will prevail whenthe test method is used in practice.10. Materials10.1 The term 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
40、 lower levels of the property.10.2 The ILS should include a minimum of three differentmaterials each with a different 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 diffe
41、rprimarily in the differing levels of the property being assessedby the test method. When it is known, or suspected, thatdifferent classes of materials will exhibit different levels ofprecision when tested by the test method, consideration shouldbe given to conducting separate interlaboratory studie
42、s for eachclass of material.10.4 The ILS should not be restricted to materials that arejudged to be exceptionally qualified for the ILS. Precisionestimates for a test method should be obtained throughconditions where materials are competent for measurement ofthe property-under-test under conditions
43、that will prevail whenthe test method is used in practice.10.5 If more precise information is required about materialsthat are not so competent for measurement of the propertybeing tested, those laboratories directly involved with thematerial in question must conduct interlaboratory studiesspecifica
44、lly aimed at the material of interest.11. Number of Test Results per Material11.1 The minimum number of test results 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 det
45、ermined by the TaskGroup, based upon the desired level of tolerance and theanticipated variation of test results from the test method.12. Protocol12.1 Prepare a written protocol containing instructions forthe participating laboratories to follow. Clearly identify thespecific version of the test meth
46、od being studied. If the testmethod allows options in apparatus or procedure, clearlyspecify which option has been selected 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
47、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 t
48、o the task group to allow them to prepare the finalresearch report on the ILS.12.4 Supply data sheets for each material for recording theraw data as observations are made, or if it would be moreconvenient for the participating laboratory, specify the format,including the number of significant digits
49、 to be recorded, of thedata to be returned to the coordinator.CONDUCTING THE TESTING PHASE OF THE ILS13. Full Scale Run13.1 Material Preparation and Distribution:13.1.1 Sample Preparation and LabelingPrepare enoughmaterial to supply 50 % more than needed by the number oflaboratories committed to the ILS. Label each test specimenwith the laboratory number and a letter designator referring tothe material. Thus, if 8 laboratories were participating in a testconcerning 6 levels of material (perhaps different colors of thesame material), then specimens would be labeled from 1A
