1、Designation: D7778 12Standard Guide forConducting an Interlaboratory Study to Determine thePrecision of a Test Method1This standard is issued under the fixed designation ; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of
2、 last revision. A number in parentheses indicates the year of last reapproval. A superscriptepsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide describes the procedures for planning andconducting an interlaboratory study (ILS) of a test method usedin
3、 Petroleum Products and Lubricants Committee D02 ofASTM for the purpose of estimating repeatability and repro-ducibility of the test method in accordance with ASTM Formand Style requirements.1.2 This guide is concerned with the management of the ILSand intended to provide guidance for the planning s
4、tage andensure the process, logistics, and tools are identified and agreedupon in advance.1.2.1 Selection of the samples and the impact of sampleselection on the final scope of the test methodboth the rangeof materials covered in the scope and precision sections and themeasurement range covered in t
5、he precision sectionareimportant, and careful consideration needs to be given to theseaspects before an ILS is launched.1.3 This guide does not concern itself with the developmentof test methods but rather with gathering the informationneeded for a test method precision statement.1.4 This guide is c
6、oncerned with test methods which yield asingle numerical figure as the test result, although the singlefigure may be the result of a calculation from a set ofmeasurements.1.5 This guide is designed for tests of properties that arestable, such that bulk samples can be homogenized andsub-samples can b
7、e prepared that will be identical and stablefor the duration of the ILS testing period. This guide is notdesigned for unstable properties or for properties that make itdifficult to obtain stable, representative samples for an ILSconducted at multiple laboratory sites.1.6 This guide represents the su
8、ggested practices for atypical precision study. Individual subcommittees may modifythis approach as their expertise directs.1.7 This guide is voluntary, and thus, is not required for anapproved precision study.2. Referenced Documents2.1 ASTM Standards:2D130 Test Method for Corrosiveness to Copper fr
9、om Petro-leum Products by Copper Strip TestD4306 Practice for Aviation Fuel Sample Containers forTests Affected by Trace ContaminationD5854 Practice for Mixing and Handling of Liquid Samplesof Petroleum and Petroleum ProductsD6300 Practice for Determination of Precision and BiasData for Use in Test
10、Methods for Petroleum Products andLubricantsD6708 Practice for Statistical Assessment and Improvementof Expected Agreement Between Two Test Methods thatPurport to Measure the Same Property of a MaterialD6792 Practice for Quality System in Petroleum Productsand Lubricants Testing LaboratoriesE177 Pra
11、ctice for Use of the Terms Precision and Bias inASTM Test MethodsE178 Practice for Dealing With Outlying ObservationsE456 Terminology Relating to Quality and StatisticsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE1169 Practice for Conducting Rugged
12、ness Tests2.2 ISO/IEC Standards:3ISO/IEC Guide 30 Terms and Definitions Used in Connec-tion with Reference MaterialsISO/IEC Guide 17025 General Requirements for the Com-petence of Testing and Calibration Laboratories3. Terminology3.1 Definitions:1This test method is under the jurisdiction of ASTM Co
13、mmittee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.94.01 on Task Group A: Quality Assurance and Quality Control.Current edition approved April 15, 2012. Published June 2012. DOI: 10.1520/D777812.2For referenced ASTM standards, visit the ASTM website,
14、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.3Available from Available from Aerospace Industries Association of America,Inc. (AIA), 1000 Wilson Blvd., Suite 1700,
15、 Arlington, VA 22209-3928, http:/www.aia-aerospace.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.1 accuracy, ncloseness of agreement between an in-dividual test result and an accepted reference value. E4563.1.2 bias, ndiffer
16、ence between the population mean ofthe test results and an accepted reference value. E4563.1.3 outlier, nobservation that appears to deviate mark-edly from the other observations of the sample (also referred toas extreme result, outlying or doubtful observation, or aberrantvalue. E1783.1.4 precision
17、, ncloseness of agreement among test re-sults obtained under prescribed conditions. E4563.1.5 reference material, nmaterial or substance, one ormore of whose property values are sufficiently homogenousand well established to be used for the calibration of anapparatus, the assessment of a measurement
18、 method, or forassigning values to other materials. E1773.1.6 repeatability, nquantitative expression of the ran-dom error associated with a single operator in a givenlaboratory obtaining repetitive results by applying the same testmethod with the same apparatus under constant operatingconditions on
19、 identical test material within a short interval oftime on the same day. It is defined as the difference betweentwo such results at the 95% confidence level. D6792, E1773.1.7 reproducibility, nquantitative expression of the ran-dom error associated with different operators from differentlaboratories
20、, using different apparatus, each obtaining a singleresult by applying the same method on an identical test sample.It is defined as the 95% confidence limit for the differencebetween two such single and independent results. D6792, E1773.1.8 trueness, ncloseness of agreement between thepopulation mea
21、n of the measurements or the test results and anaccepted reference value. E4564. Summary of Guide4.1 The procedure presented in this guide consists of fivebasic steps:(1) Planning an interlaboratory study (including objectivesand expected outcome).(2) Disclosure of plan details (participants, equipm
22、ent,samples, logistics).(3) Approval by membership.(4) Guiding the testing phase of the study and collectingtest data results.(5) Post validation that the ILS was executed in accordanceto the agreed plan.4.1.1 This guide does not address the data analysis tech-niques. For details of such analysis te
23、chniques refer to PracticeD6300 and E691, or other technically equivalent documents.4.1.2 The relevant subcommittee is the sole arbiter oftechnical equivalence.5. Significance and Use5.1 All ASTM standard test methods are required to includestatements on precision and bias. To obtain such data it is
24、necessary to conduct an interlaboratory study. This document isdesigned to provide a brief overview of the steps necessary inan ILS and to suggest an appropriate sequence in carrying outthese steps.5.1.1 Qualitative tests such as Test Method D130 coppercorrosion may not require an ILS.6. Planning an
25、 Interlaboratory Study6.1 Suggested steps in an ILS are given in Table 1.6.2 Support for conducting the ILS is available from ASTMthrough its Interlaboratory Studies Office (ILSastm.org).Individuals involved in conducting an ILS are listed below.6.2.1 “Support” does not include financial support for
26、 newor alternate equipment or procedure beyond sampling andshipping materials to the participants.6.2.2 A Task Force should be formed consisting at aminimum of the method developers, users and ASTM statisti-cian. Based on the objectives of the ILS, this task force shouldhave the overall responsibili
27、ty for the design, disclosure, andexecution of the ILS. The Task Force is charged with thedevelopment of an ILS plan that includes scope and purpose,funding, staffing, participants (equipment structure), sampletypes, tests required, special instructions, reporting form, andsample distribution, parti
28、cipant protocol, and a questionnaireand statistical tools to be used, and criteria for acceptance ofresults.6.2.3 An ILS Coordinator should be appointed as an overallperson responsible for the distribution of materials and proto-cols to the laboratories, and receive the test results from thelaborato
29、ries. Eventually this person should be responsible forall aspects of conducting the ILS, and writing the researchreport.6.2.3.1 A running activity record may be useful to bemaintained by the ILS Coordinator to overview the progress ofthe ILS activity.6.2.4 StatisticianThe Task Force should obtain th
30、e ser-vices of a statistician who is familiar with the protocols used inASTM for precision calculations during the planning stage forinput towards the design of the ILS, material selection,establishment of the statistical tools to be used, acceptancecriteria, and testing protocol. This person may be
31、 a member ofthe Task Force. This person should also assist the task group ininterpreting the results of the data analysis.TABLE 1 Sequence of an Interlaboratory StudySequence Procedure Section Number in thisGuide1 Select ILS membership 6.2.22 Prepare Basic Design 6.33 Specify Test Method(s) 6.44 Lis
32、t ParticipatingLaboratories6.55 List Materials 6.66 Number of Test Resultsper Test Material perLab6.77 Provide Protocol 6.88 Ruggedness Study(Pilot Run)7 and 89 Full Scale Run 910 Data Handling 1011 Data Presentation 1112 Prepare Study Report 12D7778 1226.2.4.1 The statistical software available fro
33、m D02 Com-mittee can help in these calculations, but it is highly recom-mended that this work be done by, or under the oversight of thestatistician engaged in 6.2.4.6.3 Basic DesignThe design should be kept as simple aspossible in order to obtain estimates of within- and between-laboratory variabili
34、ty that are free of secondary effects. Thebasic design is represented by a two-way classification table inwhich the rows represent the laboratories, the columns repre-sent the materials, and each cell (that is, the intersection of arow with a column) contains the test results obtained by aparticular
35、 laboratory on a particular material. See Table 2 forillustration where x and y are the test results obtained on thesame materials by the same operator from each laboratory.6.3.1 Samples to be tested shall be presented as a singleseries of test samples, requiring only a single analysis persample. Bo
36、th the material identification and the correspondingduplicate shall be blinded such that the tester does not know thematerial identification of the test sample, nor its correspondingduplicate run. An example of a randomized series for the ILSdesign in Table 2 is presented in Table 3. If this singler
37、andomized series approach is not possible, then blind repeatsof the same material(s) should be embedded among thesamples provided. The blind samples should represent thematerials used in the scope of the test method and concentra-tion range for which the method is applicable. At the least, theblind
38、duplicates should include a range of easy and difficultsamples and include the full sample matrix in the sample set.By including only easy samples in blind testing or the full ILSfor that matter, the resulting precision may demonstrate betterrepeatability than otherwise would be found in practice.6.
39、3.2 The randomness of testing samples is so importantthat this has to be a requirement, not just a good practice. Theactual duplicates run for each test material shall be randomizedwithin the series.6.4 Test Method A valid test method is required that hasbeen developed in one or more competent labor
40、atories andstudied in a pilot ILS (see Section 8). This draft method shoulddescribe the test procedure in terms that the steps can beunequivocally followed in a typical laboratory by competentpersonnel with the knowledge of the materials and the propertyto be tested. The test conditions that affect
41、the test resultsappreciably should be identified and the proper degree ofcontrol of sample handling and the test conditions be specifiedin the description of the test procedure. The test method shouldspecify calibration procedure and its frequency and the formatfor reporting the test results.6.5 Lab
42、oratoriesAn ILS should ideally include enoughlaboratories to produce a reproducibility estimate with at least30 degrees of freedom. See Practice D6300 for further guid-ance. It is important that a reasonable cross section of thepopulation of qualified laboratories be represented in the ILS.Special a
43、ttention is required to ensure that at least 75% of theparticipants represent product manufacturer laboratories orthird party commercial independent testing laboratories, orboth. Take care to ensure that the population is random and notbiased towards special interest participants such as equipmentve
44、ndors. Vendor participation shall be managed carefully so asnot to bias the data population.6.5.1 The final statement of precision of a test method shallnot be based on fewer than six laboratories with acceptable testresults for each material. More than 7 or 8 laboratories shouldparticipate, prefera
45、bly a minimum of 10 laboratories in casesome data is unacceptable and data from one or more labora-tories has to be excluded from the data evaluation.6.5.2 Any laboratory considered qualified to run the testroutinely should be encouraged to participate in the ILS. Inorder to obtain an adequate numbe
46、r of participating laborato-ries, the ILS study should be publicized through trade maga-zines (if feasible), meetings, broadcast through pertinentASTM committees, etc.6.5.3 “Qualified” above implies proper laboratory facilitiesand testing equipment, competent operators, familiar with thetest method,
47、 a reputation for reliable testing work, and suffi-cient time and interest to perform the task.6.5.3.1 A good gauge of a laboratories competence can beestimated by its compliance with ISO 17025 or Practice D6792laboratory quality management standards.6.5.4 If a laboratory is not familiar with the te
48、st method, itshould do several runs on available materials so all thedifficulties are worked out before participating in the actualILS.6.5.4.1 Analysts and laboratories new to the Test Methodshould be encouraged to document any aspects of the TestMethod that are unclear or ambiguous so the wording o
49、f theTest Method, especially the procedure, can be clarified toremove ambiguities.6.5.5 The ILS should not be restricted to a group oflaboratories judged to be exceptionally qualified and equippedfor the ILS. This can lead to extremely precise data whichcannot be replicated later on when the test method is used ingeneral laboratories. Precision estimates in a standard testmethod should reflect real-world situation existing at the timeof the ILS.TABLE 2 Basic Design of an Interlaboratory StudyLaboratoryMaterialsABCDEFGHIAxxxxxxxxxyyyyyyyyyBCxxxxxxxxxyyyyyyyyyDD7778
