ASTM_D_2906_-_97_2002.pdf

Designation:D 2906 97(Reapproved 2002)Standard Practice forStatements on Precision and Bias for Textiles1This standard is issued under the fixed designation D 2906;the number immediately following the designation indicates the year oforiginal adoption or,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.INTRODUCTIONWork was begun inAugust 1966 on recommendations for statements on precision and accuracy.Thefirst recommendations were issued asASTMD-13 White Paper,Statements on Precision andAccuracy,MARK I,December 1968,prepared by Subcommittee C-6 on Editorial Policy and Review.After adecision that the recommendations should be a recommended practice under the responsibility ofSubcommittee D13.93,Sampling,Presentation and Interpretation of Data,the recommendations wererevised and published as Practice D 2906 70 T.Information was added in Practice D 2906 73 on methods(1)for which precision has not beenestablished,(2)for which test results are not variables,and(3)for which statements are based onanother method.Practice D 2906 74 was expanded to include test methods in which test results arebased on the number of successes or failures in a specified number of observations or on the numberof defects or instances counted in a specified interval of time or in a specified amount of material.Thepresent text provides for a nontechnical summary at the beginning of recommended texts based onnormal distributions or on transformed data and for a more positive statement on accuracy when thetrue value of a property can be defined only in terms of a test method.In 1984,changes were introduced to replace the term“accuracy”with“bias”as directed in the May1983 edition of Form and Style for ASTM Standards.1.Scope1.1 This practice serves as a guide for using the informationobtained as directed in Practice D 2904 or obtained by otherstatistical techniques from other distributions,to prepare state-ments on precision and bias in ASTM methods prepared byCommittee D-13.The manual on form and style for standardsspecifies that statements on precision and bias be included intest methods.2Committee D-13 recommends at least a state-ment about single-operator precision in any new test method,or any test method not containing a precision statement that isput forward for 5-year approval,in both instances with acomplete statement at the next reapproval.If a provisional testmethod is proposed,at least a statement on single-operatorprecision is expected.1.2 The preparation of statements on precision and biasrequires a general knowledge of statistical principles includingthe use of components of variance estimated from an analysisof variance.Instructions covering such calculations are avail-able in Practice D 2904 or in any standard text(1,2,3,4,and5).31.3 The instructions in this practice are specifically appli-cable to test methods in which test results are based(1)on themeasurement of variables,(2)on the number of successes orfailures in the specified number of observations,(3)on thenumber of defects or incidents counted in a specified interval orin a specified amount of material,and(4)on the presence orabsence of an attribute in a test result(a go,no-go test).Instructions are also included for methods of test for whichprecision has not yet been estimated or for which precision andaccuracy have been reported in another method of test.Forobservations based on the measurement of variables,theinstructions of this practice specifically apply to test results thatare the arithmetic average of individual observations.Withqualified assistance,the same general principles can be appliedto test results that are based on other functions of the data suchas standard deviations.1This practice is under the jurisdiction ofASTM Committee D13 on Textiles andis the direct responsibility of Subcommittee D13.93 on Statistics.Current edition approved Nov.10,1997.Published August 1998.Originallypublished as D 2906 70 T.Last previous edition D 2906 91.2Form and Style for ASTM Standards,May 1983,available from AmericanSociety for Testing and Materials,100 Barr Harbor Drive,West Conshohocken,PA19428.3The boldface numbers in parentheses refer to the list of references at the end ofthis practice.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.1.4 This standard includes the following sections:Section No.Attributes,Statements Based on15Binomial Distributions,Calculations for9Binomial Distributions,Statements Based on13Categories of Data7Computer Preparation of Statements Based on Normal or Trans-formed Data12Normal Distributions and Transformed Data,Calculations for8Normal Distributions and Transformed Data,Statements Based on11Poisson Distributions,Calculations for10Poisson Distributions,Statements Based on14Precision and Bias Based on Other Methods16Precision N