Designation:D7729−12StandardPracticeforDeterminingandExpressingPrecisionofMeasurementResults,intheAnalysisofWater,asRelativeStandardDeviation,UtilizingDQCALCSoftware1ThisstandardisissuedunderthefixeddesignationD7729;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1ThisPracticedescribesaprocedurefordevelopingagraphicalmodelofrelativestandarddeviationvsconcentrationforaanalyticalmethodsusedintheanalysisofwater(methodsthataresubjecttonon-additiverandomerrors)forthepurposeofassigningastatementofnoiseorrandomnesstoanalyticalresults(commonlyreferredtoasaprecisionstatement),ineitheramanualoranautomatedfashion.1.2DataanalysisandmodelingisdonewithD19AdjunctDQCALC(anExcelbasedtool).1.3ThevaluesstatedinSIunitsaretoberegardedasthestandard.Thevaluesgiveninparenthesesareforinformationonly.1.4Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.2.Introduction2.1Anunderstandingoftheuncertaintyassociatedwithmeasurementresultsisnecessaryforevaluatingtheutilityofthoseresults.Withoutareporteduncertaintyestimate,usersofmeasurementresultsareunabletodetermineifthedataaresufficientlypreciseforanyspecificdatause.2.2MeasurementUncertaintyismostgenerallyunderstoodtobe“aparametercharacterizingthedispersionofthequantityvaluesbeingattributedtoameasurand”(fromInternationalVocabularyofMetrology(VIM)2.26).Thisdefinitioncanbeimplementedasanexpression(“uncertaintystatement”)asso-ciatedwithanreportedmeasurementthatrepresentsthestatisticallybased(TypeAestimate)dispersionofexperimentalresultsaroundareportedvalue.2.3Thereisnouniversallyagreeduponformatornomen-clatureforuncertaintystatements.Thelitera...
