1、Designation: D7778 12D7778 15 An American National StandardStandard Guide forConducting an Interlaboratory Study to Determine thePrecision of a Test Method1This standard is issued under the fixed designation D7778; 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 () indicates an editorial change since the last revision or reapproval.1. Scope Scope*1.1 This guide describes the procedures for planning and conducting an
3、interlaboratory study (ILS) of a test method used inPetroleum Products and Lubricants Committee D02 ofASTM for the purpose of estimating repeatability and reproducibility of thetest method in accordance with ASTM Form and Style requirements.1.2 This guide is concerned with the management of the ILS
4、and intended to provide guidance for the planning stage and ensurethe process, logistics, and tools are identified and agreed upon in advance.1.2.1 Selection of the samples and the impact of sample selection on the final scope of the test methodboth the range ofmaterials covered in the scope and pre
5、cision sections and the measurement range covered in the precision sectionare important,and careful consideration needs to be given to these aspects before an ILS is launched.1.3 This guide does not concern itself with the development of test methods but rather with gathering the information neededf
6、or a test method precision statement.1.4 This guide is concerned with test methods which yield a single numerical figure as the test result, although the single figuremay be the result of a calculation from a set of measurements.1.5 This guide is designed for tests of properties that are stable, suc
7、h that bulk samples can be homogenized and sub-samplescan be prepared that will be identical and stable for the duration of the ILS testing period. This guide is not designed for unstableproperties or for properties that make it difficult to obtain stable, representative samples for an ILS conducted
8、 at multiple laboratorysites.1.6 This guide represents the suggested practices for a typical precision study. Individual subcommittees may modify thisapproach as their expertise directs.1.7 This guide is voluntary, and thus, is not required for an approved precision study.2. Referenced Documents2.1
9、ASTM Standards:2D130 Test Method for Corrosiveness to Copper from Petroleum Products by Copper Strip TestD4306 Practice for Aviation Fuel Sample Containers for Tests Affected by Trace ContaminationD5854 Practice for Mixing and Handling of Liquid Samples of Petroleum and Petroleum ProductsD6300 Pract
10、ice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and LubricantsD6708 Practice for Statistical Assessment and Improvement of Expected Agreement Between Two Test Methods that Purportto Measure the Same Property of a MaterialD6792 Practice for Quality Syst
11、em in Petroleum Products and Lubricants Testing LaboratoriesE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsE178 Practice for Dealing With Outlying ObservationsE456 Terminology Relating to Quality and StatisticsE691 Practice for Conducting an Interlaboratory Study to Determ
12、ine the Precision of a Test MethodE1169 Practice for Conducting Ruggedness Tests1 This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.94.01 on Task Group A: Quality Assurance
13、 and Quality Control.Current edition approved April 15, 2012April 1, 2015. Published June 2012May 2015. Originally approved in 2012. Last previous edition approved in 2012 as D7778 12.DOI: 10.1520/D777812.10.1520/D7778-15.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contac
14、tASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been
15、made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*
16、A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States12.2 ISO/IEC Standards:3ISO/IEC Guide 30 Terms and Definitions Used in Connection with Reference MaterialsISO/IEC Guide 170
17、25 General Requirements for the Competence of Testing and Calibration Laboratories3. Terminology3.1 Definitions:3.1.1 accuracy, ncloseness of agreement between an individual test result and an accepted reference value. E4563.1.2 bias, ndifference between the population mean of the test results and a
18、n accepted reference value. E4563.1.3 outlier, nobservation that appears to deviate markedly from the other observations of the sample (also referred to asextreme result, outlying or doubtful observation, or aberrant value. E1783.1.4 precision, ncloseness of agreement among test results obtained und
19、er prescribed conditions. E4563.1.5 reference material, nmaterial or substance, one or more of whose property values are sufficiently homogenous and wellestablished to be used for the calibration of an apparatus, the assessment of a measurement method, or for assigning values to othermaterials. E177
20、3.1.6 repeatability, nquantitative expression of the random error associated with a single operator in a given laboratoryobtaining repetitive results by applying the same test method with the same apparatus under constant operating conditions onidentical test material within a short interval of time
21、 on the same day. It is defined as the difference between two such results atthe 95% confidence level. D6792, E1773.1.7 reproducibility, nquantitative expression of the random error associated with different operators from differentlaboratories, using different apparatus, each obtaining a single res
22、ult by applying the same method on an identical test sample. Itis defined as the 95% confidence limit for the difference between two such single and independent results. D6792, E1773.1.8 trueness, ncloseness of agreement between the population mean of the measurements or the test results and an acce
23、ptedreference value. E4564. Summary of Guide4.1 The procedure presented in this guide consists of five basic steps:(1) Planning an interlaboratory study (including objectives and expected outcome).(2) Disclosure of plan details (participants, equipment, samples, logistics).(3) Approval by membership
24、.(4) Guiding the testing phase of the study and collecting test data results.(5) Post validation that the ILS was executed in accordance to the agreed plan.4.1.1 This guide does not address the data analysis techniques. For details of such analysis techniques refer to Practice D6300and E691, or othe
25、r technically equivalent documents.4.1.2 The relevant subcommittee is the sole arbiter of technical equivalence.5. Significance and Use5.1 AllASTM standard test methods are required to include statements on precision and bias. To obtain such data it is necessaryto conduct an interlaboratory study. T
26、his document is designed to provide a brief overview of the steps necessary in an ILS andto suggest an appropriate sequence in carrying out these steps.5.1.1 Qualitative tests such as Test Method D130 copper corrosion may not require an ILS.6. Planning an Interlaboratory Study6.1 Suggested steps in
27、an ILS are given in Table 1.6.2 Support for conducting the ILS is available from ASTM through 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 new or alternate equipment or procedure bey
28、ond sampling and shippingmaterials to the participants.6.2.2 A Task Force should be formed consisting at a minimum of the method developers, users and ASTM statistician. Basedon the objectives of the ILS, this task force should have the overall responsibility for the design, disclosure, and executio
29、n of theILS. The Task Force is charged with the development of an ILS plan that includes scope and purpose, funding, staffing, participants(equipment structure), sample types, tests required, special instructions, reporting form, and sample distribution, participantprotocol, and a questionnaire and
30、statistical tools to be used, and criteria for acceptance of results.3 Available from Available from Aerospace Industries Association of America, Inc. (AIA), 1000 Wilson Blvd., Suite 1700, Arlington, VA 22209-3928, http:/www.aia-aerospace.org.D7778 1526.2.3 An ILS Coordinator should be appointed as
31、an overall person responsible for the distribution of materials and protocolsto the laboratories, and receive the test results from the laboratories. Eventually this person should be responsible for all aspectsof conducting the ILS, and writing the research report.6.2.3.1 A running activity record m
32、ay be useful to be maintained by the ILS Coordinator to overview the progress of the ILSactivity.6.2.4 StatisticianThe Task Force should obtain the services of a statistician who is familiar with the protocols used in ASTMfor precision calculations during the planning stage for input towards the des
33、ign of the ILS, material selection, establishment ofthe statistical tools to be used, acceptance criteria, and testing protocol. This person may be a member of the Task Force. Thisperson should also assist the task group in interpreting the results of the data analysis.6.2.4.1 The statistical softwa
34、re available from D02 Committee can help in these calculations, but it is highly recommended thatthis work be done by, or under the oversight of the statistician engaged in 6.2.4.6.3 Basic DesignThe design should be kept as simple as possible in order to obtain estimates of within- and between-labor
35、atory variability that are free of secondary effects. The basic design is represented by a two-way classification table in whichthe rows represent the laboratories, the columns represent the materials, and each cell (that is, the intersection of a row with acolumn) contains the test results obtained
36、 by a particular laboratory on a particular material. See Table 2 for illustration where xand y are the test results obtained on the same materials by the same operator from each laboratory.6.3.1 Samples to be tested shall be presented as a single series of test samples, requiring only a single anal
37、ysis per sample. Boththe material identification and the corresponding duplicate shall be blinded such that the tester does not know the materialidentification of the test sample, nor its corresponding duplicate run.An example of a randomized series for the ILS design in Table2 is presented in Table
38、 3. If this single randomized series approach is not possible, then blind repeats of the same material(s) shouldbe embedded among the samples provided. The blind samples should represent the materials used in the scope of the test methodand concentration range for which the method is applicable. At
39、the least, the blind duplicates should include a range of easy anddifficult samples and include the full sample matrix in the sample set. By including only easy samples in blind testing or the fullILS for that matter, the resulting precision may demonstrate better repeatability than otherwise would
40、be found in practice.6.3.2 The randomness of testing samples is so important that this has to be a requirement, not just a good practice. The actualduplicates run for each test material shall be randomized within the series.6.4 Test Method A valid test To establish initial precision statements for a
41、 new test method, a draft of the test method isrequired that has been developed in one or more competent laboratories and studied in a pilot ILS (see Section 8). This draftmethod should describe the test procedure in terms that the steps can be unequivocally followed in a typical laboratory bycompet
42、ent personnel with the knowledge of the materials and the property to be tested.The test conditions that affect the test resultsTABLE 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.
43、44 List 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 12TABLE 2 Basic Design of an Interlaboratory StudyL
44、aboratory MaterialsA B C D E F G H IA x x x x x x x x xy y y y y y y y yB x x x x x x x x xy y y y y y y y yC x x x x x x x x xy y y y y y y y yD x x x x x x x x xy y y y y y y y yD7778 153appreciably should be identified and the proper degree of control of sample handling and the test conditions be
45、 specified in thedescription of the test procedure. The test method should specify calibration procedure and its frequency and the format forreporting the test results.6.4.1 Reevaluation of Existing Precision StatementsTo reevaluate existing precision statements for test methods, all aspectsof the e
46、xisting test method that are not intended to be revised shall be followed. Intended revisions to the test method shall behighlighted in the test method and explicitly stated to the participants.6.4.1.1 ILS Execution ProtocolThe procedures and special instructions provided in the ILS protocol for par
47、ticipation shall notintroduce restrictions or controls in the execution of the method that are not in the normal execution of the method being evaluated.6.4.1.2 VariablesAll variables in the test method that are intended to be variables shall be left as variables in the ILS. Toremove, control, or se
48、t limits on factors that are not intended to be controlled in the normal usage of the test method in theexecution of the ILS will result in the precision being overly optimistic, and as such precision statements thus generated will likelybe unattainable by users in the normal usage of the method.6.5
49、 LaboratoriesAn ILS should ideally include enough laboratories to produce a reproducibility estimate with at least 30degrees of freedom. See Practice D6300 for further guidance. It is important that a reasonable cross section of the population ofqualified laboratories be represented in the ILS. Special attention is required to ensure that at least 75% of the participants representproduct manufacturer laboratories or third party commercial independent testing laboratories, or both. Take care to ensure that thepopulation is random and not biased towards specia
