Designation:E122−09´1AnAmericanNationalStandardStandardPracticeforCalculatingSampleSizetoEstimate,WithSpecifiedPrecision,theAverageforaCharacteristicofaLotorProcess1ThisstandardisissuedunderthefixeddesignationE122;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.ThisstandardhasbeenapprovedforusebyagenciesoftheU.S.DepartmentofDefense.ε1NOTE—Editorialcorrectionsweremadeto8.4.1.2inNovember2011.1.Scope1.1Thispracticecoverssimplemethodsforcalculatinghowmanyunitstoincludeinarandomsampleinordertoestimatewithaspecifiedprecision,ameasureofqualityforalltheunitsofalotofmaterial,orproducedbyaprocess.Thispracticewillclearlyindicatethesamplesizerequiredtoestimatetheaveragevalueofsomepropertyorthefractionofnonconform-ingitemsproducedbyaproductionprocessduringthetimeintervalcoveredbytherandomsample.Iftheprocessisnotinastateofstatisticalcontrol,theresultwillnothavepredictivevalueforimmediate(future)production.Thepracticetreatsthecommonsituationwherethesamplingunitscanbeconsideredtoexhibitasingle(overall)sourceofvariability;itdoesnottreatmulti-levelsourcesofvariability.2.ReferencedDocuments2.1ASTMStandards:2E456TerminologyRelatingtoQualityandStatistics3.Terminology3.1Definitions—Unlessotherwisenoted,allstatisticaltermsaredefinedinTerminologyE456.3.2Symbols—Symbolsusedinallequationsaredefinedasfollows:E=themaximumacceptabledifferencebetweenthetrueaverageandthesampleaverage.e=E/µ,maximumacceptabledifferenceexpressedasafractionofµ.f=degreesoffreedomforastandarddeviationestimate(7.5).k=thetotalnumberofsamplesavailablefromthesameorsimilarlots.µ=lotorprocessmeanorexpectedvalueofX,theresultofmeasuringalltheunitsinthelotorprocess.µ0=anadvanceestimateofµ.N=sizeofthelot.n=sizeofthesampletakenfromalotorprocess.nj=sizeofsamplej.nL=sizeofthesamplefromafinitelot(7.4).p'=fractiono...
