ASTM_E_2655_-_14.pdf

Designation:E265514An American National StandardStandard Guide forReporting Uncertainty of Test Results and Use of the TermMeasurement Uncertainty in ASTM Test Methods1This standard is issued under the fixed designation E2655;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()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This guide provides concepts necessary for understand-ing the term“uncertainty”when applied to a quantitative testresult.Several measures of uncertainty can be applied to agiven measurement result;the interpretation of some of thecommon forms is described.1.2 This guide describes methods for expressing test resultuncertainty and relates these to standard statistical methodol-ogy.Relationships between uncertainty and concepts of preci-sion and bias are described.1.3 This guide also presents concepts needed for a labora-tory to identify and characterize components of method per-formance.Elements that an ASTM method can include toprovide guidance to the user on estimating uncertainty for themethod are described.1.4 The system of units for this guide is not specified.Dimensional quantities in the guide are presented only asillustrations of calculation methods and are not binding onproducts or test methods treated.1.5 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-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2E29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE122 Practice for Calculating Sample Size to Estimate,WithSpecified Precision,the Average for a Characteristic of aLot or ProcessE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE456 Terminology Relating to Quality and StatisticsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE1402 Guide for Sampling DesignE2554 Practice for Estimating and Monitoring the Uncer-tainty of Test Results of a Test Method Using ControlChart TechniquesE2586 Practice for Calculating and Using Basic Statistics2.2 Other Standard:ISO/IEC 17025 General Requirements for the Competenceof Testing and Calibration Laboratories33.Terminology3.1 Definitions:3.1.1 Additional statistical terms are defined in TerminologyE456.3.1.2 accepted reference value,na value that serves as anagreed-upon reference for comparison,and which is derivedas:(1)a theoretical or established value,based on scientificprinciples,(2)an assigned or certified value,based on experi-mental work of some national or international organization,or(3)a consensus or certified value,based on collaborativeexperimental work under the auspices of a scientific orengineering group.E1773.1.3 error of result,na test result minus the acceptedreference value of the characteristic.3.1.4 expanded uncertainty,U,nuncertainty reported as amultiple of the standard uncertainty.3.1.5 random error of result,na component of the errorthat,in the course of a number of test results for the samecharacteristic,varies in an unpredictable way.3.1.5.1 DiscussionUncertainty due to random error can bereduced by averaging multiple test results.3.1.6 sensitivity coeffcient,ndifferential effect of thechange in a factor on the test result.1This 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 approved Oct.1,2014.Published October 2014.Originallyapproved in 2008.Last previous edition approved in 2008 as E2655 08.DOI:10.1520/E2655-14.2For 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 to 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.1.7 standard uncertainty,u,nuncertainty reported as thestandard deviation of the estimated value of the quantitysubject to measurement.3.1.8 systematic error of result,na component of the errorthat,in the course of a number of test results for the samecharacteristic,remains constant or varies in a predictable way.3.1.8.1 DiscussionSystematic errors and their causes maybe known or unknown.When causes are known,systematicerror can sometimes be reduced by incorporating correctionsinto the calculation of the test result.3.1.9 uncertainty,nan indication of the magnitude of error