1、Designation: E 1488 09An American National StandardStandard Guide forStatistical Procedures to Use in Developing and ApplyingTest Methods1This standard is issued under the fixed designation E 1488; the number immediately following the designation indicates the year oforiginal adoption or, in the cas
2、e 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 guide identifies statistical procedures for use indeveloping new test methods or revis
3、ing or evaluating existingtest methods, or both.1.2 This guide also cites statistical procedures especiallyuseful in the application of test methods.2. Referenced Documents2.1 ASTM Standards:2E 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 178 Practice for Dealing With Ou
4、tlying ObservationsE 456 Terminology Relating to Quality and StatisticsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE 1169 Practice for Conducting Ruggedness TestsE 2282 Guide for Defining the Test Result of a Test MethodE 2489 Practice for Statist
5、ical Analysis of One-Sample andTwo-Sample Interlaboratory Proficiency Testing ProgramsE 2554 Practice for Estimating and Monitoring the Uncer-tainty of Test Results of a Test Method in a SingleLaboratory Using a Control Sample ProgramE 2586 Practice for Calculating and Using Basic StatisticsE 2587 P
6、ractice for Use of Control Charts in StatisticalProcess Control2.2 ISO Standards:ISO 17025 General Requirements for the Competence ofTesting and Calibration Laboratories3ISO Guide to the Expression of Uncertainty in Measure-ment33. Terminology3.1 Definitions:3.1.1 bias, nthe difference between the e
7、xpectation of thetest results and an accepted reference value. E 1773.1.1.1 DiscussionStatistical procedures include the sam-pling considerations or the experiment design for the collectionof data, or both, and the numerical and graphical approaches tosummarize and analyze the collected data.3.1.2 c
8、oeffcient of variation, CV, nfor a nonnegativecharacteristic, the ratio of the standard deviation to the meanfor a population or sample. E 25863.1.3 component of variance, na part of a total varianceidentified with a specified source of variability.3.1.4 control chart, nchart on which are plotted a
9、statis-tical measure of a subgroup versus time of sampling along withlimits based on the statistical distribution of that measure so asto indicate how much common, or chance, cause variation isinherent in the process or product. E 25873.1.5 observation, nthe process of obtaining informationregarding
10、 the presence or absence of an attribute of a testspecimen, or of making a reading on a characteristic ordimension of a test specimen. E 22823.1.6 observed value, nthe value obtained by making anobservation. E 22823.1.7 precision, nthe closeness of agreement betweenindependent test results obtained
11、under stipulated conditions.E 1773.1.8 proficiency testing, ndetermination of laboratorytesting performance by means of interlaboratory comparisons.E 24893.1.9 repeatability, nprecision under repeatability condi-tions. E 1773.1.10 repeatability conditions, nconditions where inde-pendent test results
12、 are obtained with the same method onidentical test items in the same laboratory by the same operatorusing the same equipment within short intervals of time.E 1773.1.11 repeatability limit r, nthe value below which theabsolute difference between two individual test results obtainedunder repeatabilit
13、y conditions may be expected to occur with aprobability of approximately 0.95 (95 %). E 1771This guide is under the jurisdiction of ASTM Committee E11 on Quality andStatistics and is the direct responsibility of Subcommittee E11.20 on Test MethodEvaluation and Quality Control.Current edition approve
14、d May 15, 2009. Published July 2009. Originallyapproved in 1992. Last previous edition approved in 2008 as E 1488 08a.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, refer t
15、o the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3
16、.1.12 repeatability standard deviation, n the standarddeviation of test results obtained under repeatability condi-tions. E 1773.1.13 reproducibility, nprecision under reproducibilityconditions. E 1773.1.14 reproducibility conditions, nconditions where testresults are obtained with the same method o
17、n identical testitems in different laboratories with different operators usingdifferent equipment. E 1773.1.15 reproducibility limit, R, nthe value below whichthe absolute difference between two test results obtained underreproducibility conditions may be expected to occur with aprobability of appro
18、ximately 0.95 (95 %). E 1773.1.16 reproducibility standard deviation S R, nthe stan-dard deviation of test results obtained under reproducibilityconditions. E 1773.1.17 ruggedness, ninsensitivity of a test method todepartures from specified test or environmental conditions.E 11693.1.18 ruggedness te
19、st, na planned experiment in whichenvironmental factors or test conditions are deliberately variedin order to evaluate the effects of such variation. E 11693.1.19 standard deviation, nof a population, s, the squareroot of the average or expected value of the squared deviationof a variable from its m
20、ean of a sample x, the square root ofthe sum of the squared deviations of the observed values in thesample divided by the sample size minus 1. E 25863.1.20 state of statistical control, nprocess conditionwhen only common causes are operating on the process.E 25873.1.21 statistical procedures, nthe o
21、rganized techniquesand methods used to collect, analyze, and interpret data.3.1.21.1 DiscussionStatistical procedures include thesampling considerations or the experiment design for thecollection of data, or both, and the numerical and graphicalapproaches to summarize and analyze the collected data.
22、3.1.22 test determination, nthe value of a characteristic ordimension of a single test specimen derived from one or moreobserved values. E 22823.1.23 test method, na definitive procedure that producesa test result. E 22823.1.24 test observation, nsee observation. E 22823.1.25 test result, nthe value
23、 of a characteristic obtainedby carrying out a specified test method. E 22823.1.25.1 DiscussionStatistical procedures include thesampling considerations or the experiment design for thecollection of data, or both, and the numerical and graphicalapproaches to summarize and analyze the collected data.
24、3.2 For all other formal definitions of statistical terms, seeTerminology E 456.4. Significance and Use4.1 All ASTM test methods are required to include state-ments on precision and bias.44.2 Since ASTM began to require all test methods to haveprecision and bias statements that are based on interlab
25、oratorytest methods, there has been increased concern regarding whatstatistical experiments and procedures to use during the devel-opment of the test methods. Although there exists a wide rangeof statistical procedures, there is a small group of generallyaccepted techniques that are very beneficial
26、to follow. Thisdocument is designed to provide a brief overview of theseprocedures and to suggest an appropriate sequence of carryingout these procedures.4.3 Statistical procedures often result in interpretations thatare not absolutes. Sometimes the information obtained may beinadequate or incomplet
27、e, which may lead to additional ques-tions and the need for further experimentation. Informationoutside the data is also important in establishing standards andin the interpretation of numerical results.5. Summary of Guide5.1 Outlined below is a suggested sequence of four phasesuseful in the develop
28、ment of a test method. A flowchart isprovided in Fig. 1. Such a sequence of analyses may need to bemodified in specific situations. The assistance of a qualifiedstatistician is recommended at each review phase.5.2 Design Phase:5.2.1 This phase includes the formalization of the scope andthe significa
29、nce and use sections. It may include determiningthe purpose and describing a general approach to the testmethod but usually does not involve statistical studies.5.3 Development Phase5.3.1 Studies may be conducted to evaluate the basicperformance of the method. The draft test method is preparedand sa
30、mpling requirements and the test result (see GuideE 2282) are clearly defined.5.3.2 A flow chart is extremely valuable to identify thesequence of operations involved in a test method, for example,the sampling steps required to obtain the test specimens,definition of the test determination, how a tes
31、t result is to becomputed, and running the tests on the specimens.5.4 Validation Phase5.4.1 The test method is examined for such concerns as itsstability, ruggedness, statistical control and the contributions tovariability. The completion of this phase should result inpreliminary estimates of precis
32、ion and the identification andsuggested ways to estimate potential contributors to uncer-tainty.5.4.2 Evaluation of Short Term Control of Test MethodAtest method must exhibit an ability to provide consistent resultsat least over short time periods. Preliminary studies or a pilottest should be conduc
33、ted to evaluate the short term stability ofthe test method. A small series of repeated tests should beconducted.5.4.3 Analysis of VariabilityStatistically designed experi-ments conducted in one or two laboratories can be used toassess the relative magnitudes of different sources or potentialcontribu
34、tors to variability of the test results. Such studies canprovide estimates of intermediate measures of precision.5.4.4 Ruggedness TestA ruggedness test (see PracticeE 1169) is a statistically designed experiment that helps iden-tify problems in running the test method, clarifies errors, and4See the
35、Form and Style Manual for ASTM Standards that specifies, whenpossible, precision statements shall be estimated based on the results of aninterlaboratory test program.E1488092points out possible environmental conditions, which mayadversely affect the test method or point out need for tighteningrequir
36、ements. The ruggedness test can assist in locating waysof reducing variability in the test method.5.4.5 Preliminary Estimates of PrecisionFrom the variousstudies conducted in accordance with 5.4.25.4.4, preliminaryestimates of repeatability standard deviations should be devel-oped and published in t
37、his test method. Until an interlaboratorystudy is performed, these estimates generally are considered tobe provisional. Information on how a lab should developuncertainty estimates should also be provided.5.4.6 Statistical ControlA test method must show capa-bility of performing in a consistent way
38、over time. The use ofcontrol charts (see Manual 7)4to monitor a proposed, orexisting, test method over time is one recommended way toexamine the controllability or stability of a test method. Thisstatistical control should be demonstrated in one or twolaboratories using homogeneous material (test sp
39、ecimen).5.5 Evaluation Phase:5.5.1 The test method is subjected to interlaboratory studiesto provide estimates of within-laboratory repeatability andbetween-laboratory reproducibility. Additional information issupplied from proficiency studies when conducted.5.5.2 Interlaboratory Study (ILS)In accor
40、dance withASTM Form and Style Manual, whenever feasible, an inter-laboratory study must be conducted. This procedure willprovide specific estimates of variation anticipated when usingthe test method.5.5.3 Protocol for the ILS, Practice E 691 provides a guidefor developing the ILS for the test method
41、. A first step is thewriting of an ILS Protocol, which will set out what needs to bedone before the test specimens (or test materials) are distrib-uted to the participating laboratories.5.5.4 Precision StatementsUsing the estimates of varia-tion obtained in the interlaboratory test, one may preparep
42、recision statements using Practices E 691 and E 177 orequivalent procedures.6. Development of Test Method Sampling and TestResult6.1 Proposed standards that are under development shouldbe treated in a formal manner following as many of thesuggested procedures as possible. Standards that are already
43、inexistence as approved test methods or in general practicerequire periodic review that would include selected procedures.6.2 Under DevelopmentThe development stage involvestest methods that are in the preliminary stages during whichequipment may not have been fully tested, practices are notFIG. 1 S
44、equence of StepsE1488093agreed upon, and operators have yet to be adequately trained.Often this stage also applies to standards that have not yet beenapproved.6.2.1 It is essential that tests for statistical control, rugged-ness, and variability analyses be conducted prior to anyinterlaboratory test
45、 programs.6.2.2 After all major environmental contributors have beenidentified, controlled, and incorporated into the test method,and after adequate standardized equipment is available, aninterlaboratory test can be conducted. The interlaboratory testprogram must be completed prior to the first 5-ye
46、ar review. Thecommittee should strive to have interlaboratory results as soonas possible.6.2.3 After evaluating data from ruggedness tests, variabil-ity analysis, or an interlaboratory test program, changes to thetest method may be suggested.6.2.4 If major changes are made to the test method, a repe
47、atof the various steps is usually necessary. Precision and biasstatements should reflect the most current version of the testmethod.6.3 Existing StandardsThese standards comprise testmethods that are in common use for which standard equipmentmay exist and for which experienced operators have beentra
48、ined and are available.6.3.1 Control charting, ruggedness tests, and variabilityanalyses will be useful, especially if they have not previouslybeen conducted. Such tests may provide better informationabout variation and necessary tolerances than has previouslybeen available.6.3.2 If precision estima
49、tes have not been establishedthrough an actual interlaboratory test program, then such aprogram should be initiated.7. Data and Sampling7.1 Sample Determination:7.1.1 The sampling section of a standard should indicateclearly what constitutes the primary sampling unit, how thatsampling unit is further subdivided, and how multiple testvalues are designated.7.1.2 In considering the implication of test results as theyrelate to the material, the test method should be clear as towhether the sampling method or the test is destructive ornondestr
