Designation:D4855–97(Reapproved2002)StandardPracticeforComparingTestMethods1ThisstandardisissuedunderthefixeddesignationD4855;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(e)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thispracticeprovidesaprocedureforevaluatingandcomparingtestmethodsundercontrolledconditionsusingthesamematerialstestedduringthesametimespan.Thepracticedescribeshowtoobtainandcompareestimatesonprecision,sensitivity,andbias.1.2Thispracticecoversthefollowingtopics:TopicTitleSectionnumberScope1ReferencedDocuments2Terminology3SignificanceandUse4RequirementsforMaterials5EvaluatingTestMethods6SensitivityCriterion7BasicStatisticalDesign8ExperimentalProcedure9ProcedureforComparingPrecision10EvaluatingtheBiasBetweenTestMethods11ProcedureforComparingSensitivities12Report132.ReferencedDocuments2.1ASTMStandards:D123TerminologyRelatingtoTextiles2D2905PracticeforStatementsonNumberofSpecimensforTextiles2D2906PracticeforStatementsonPrecisionandBiasforTextiles2E456TerminologyRelatingtoQualityandStatistics32.2ASTMAdjuncts:TEX-PAC4NOTE1—Tex-PacisagroupofPCprogramsonfloppydisks,availablethroughASTMHeadquarters,100BarrHarborDrive,Conshohocken,PA19428,USA.Thecalculationsforcomparingtheprecision,sensitivityandbiasoftwotestmethodscanbedoneusingoneoftheseprogramsandstatementsontherelativemeritsofthetwotestmethodsarepartoftheoutput.3.Terminology3.1Definitions:3.1.1accuracy,n—ofatestmethod,thedegreeofagree-mentbetweenthetruevalueofthepropertybeingtested(oranacceptedstandardvalue)andtheaverageofmanyobservationsmadeaccordingtothetestmethod,preferablybymanyobservers.(Seealsobiasandprecision.)3.1.1.1Discussion—Increasedaccuracyisassociatedwithdecreasedbiasrelativetothetruevalue;twomethodswithequalbiasrelativetothetruevaluehaveequalaccuracyevenifonemethodismoreprecisethantheother.Thetruevalueistheexactvalue...
