Designation:D5406−93(Reapproved2011)StandardPracticeforRubber—CalculationofProducer’sProcessPerformanceIndexes1ThisstandardisissuedunderthefixeddesignationD5406;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thispracticeprovidesacalculationprocedureandaformatforreportingtheprocessperformanceofamanufactur-ingoperationforarubberorrubberproduct.1.2Thispracticeisspecificallydesignedtobeusedfortechnicallysignificantpropertiesofthefinalproduct.2.ReferencedDocuments2.1QualityAssurancefortheChemicalandProcessIndus-tries,AmericanSocietyforQualityControl,ChemicalandProcessIndustriesDivision,ChemicalInterestCommittee,1987.23.Terminology3.1DefinitionsofTermsSpecifictoThisStandard:3.1.1commoncausevariation—thatresidualvariationin-herentinanyprocessthat(1)isoperatinginastateofstatisticalcontrol,and(2)isoperatingatsomerecognizedorascertainedleveloftechnologicalcompetence.3.1.2lowerspecificationlimit(LSL)—theproducer’smini-mumpermissiblevalueofanyrelevantmeasuredproductproperty.3.1.3Pp8producer’sprocessperformanceindex—theratioofthedifference(USL−LSL)tothetotalprocessvariation;theindexdoesnotconsiderwheretheprocessiscentered.(See7.4.)3.1.4Ppk8producer’sprocessperformanceindex—theminimumoftworatios:(1)theratioofthedifference(USL−processmean)toone-halfofthetotalprocessvaria-tion,or(2)theratioofthedifference(processmean−LSL)toone-halfofthetotalprocessvariation;themagnitudeoftheminimumindexvalue,usedwiththePp8index,indicateshowwelltheprocessmeaniscentered.(See7.5.)3.1.5specialcausevariation—thatvariationattributabletocertainspecificorassignablesourcesthathavebeen(ormaybe)discoveredthroughaninvestigationoftheprocess.3.1.6targetvalue—theaimingpointoftheprocess;thisisoften(USL+LSL)/2.3.1.7totalprocessvariation—arange,alongthemeasuredpropertyscale,defined...
