Designation:D3244−16AnAmericanNationalStandardStandardPracticeforUtilizationofTestDatatoDetermineConformancewithSpecifications1ThisstandardisissuedunderthefixeddesignationD3244;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.INTRODUCTIONThepropertiesofcommercialpetroleumproductsaremeasuredbystandardizedlaboratorytestmethodstoassesstheirconformancetospecifications.Twoormoremeasurementresultsobtainedbyperformingthesametestmethodforthesamepropertyofaspecificsampleusuallywillnotbenumericallyidentical.Therefore,thetestmethodsgenerallyincludeaparagraphontheprecisionofresults.Thisprecision(or,amoreappropriatetermisimprecision)isanexpressionofthedegreeofagreementthatcanbeexpectedbetweentheaforementionedmeasurements.Manydifficultiesthatariseinassessingconformancetospecificationsareduetotestimprecision.Becauseofthis,atruevalueofapropertycanneverbedeterminedexactly;anditisnecessarytoinferfrommeasuredvaluestherangewithinwhichthe“truevalue”islikelytolie.Themainpurposeofthispracticeistoindicatehowtestimprecisionshouldbeinterpretedrelativetospecificationlimitvalues.1.Scope*1.1Thispracticecoversguidelinesandstatisticalmethod-ologieswithwhichtwoparties,usuallyasupplierandareceiver,cancompareandcombineindependentlyobtainedtestresultstoobtainanAssignedTestValue(ATV)forthepurposeofresolvingaproductqualitydispute.1.2ThispracticedefinesatechniqueforcomparinganATVwithaspecificationlimit.1.3Thispracticeappliesonlytothosetestmethodswhichspecificallystatethattherepeatabilityandreproducibilityvaluesconformtothedefinitionsherein.1.4ThestatisticalprinciplesandmethodologyoutlinedinthispracticecanalsobeusedtoobtainanATVforspecificationconformancedecisionwhenmultipleresultsareobtainedforthesamebatchofproductwithinasinglelaboratory.Forthisapplication,siteprecision(R’)asdefinedinPractice...
