Uncertainty Pre不确定度计算

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1、UncertaintyinMeasurementKamaleldinIbrahimIsmail101/10/2002Thevariationsintheresultofameasurementwhichcanbeattributedtothepropertiesofthemeasurementsystemandthepropertiesofthequantitybeingmeasured.KamaleldinIbrahimIsmail201/10/2002UncertaintyinMeasurementThisisnotthesameasERROR.

2、Anerrorcanbecorrectedandeliminated,atleastinprinciple;UNCERTAINTYisanintrinsicpropertywhichmaybereduciblebutnevertozero.KamaleldinIbrahimIsmail301/10/2002UncertaintyinMeasurementItisnotthesameasIN-HOUSEREPRODUCIBILITYorREPEATABILITY.Theseonlymeasurethevariationsthatactuallyoccu

3、rwithinyourownlaboratory.KamaleldinIbrahimIsmail401/10/2002UncertaintyinMeasurementArealestimateofuncertaintyisaglobalestimate,i.e.itreflectsthespreadindatawhichmightbeexpectedifthesamesamplesweretested,bythesamemethod,inanylaboratorywithequipmentcalibratedtothesameaccuracyasth

4、atinyourlaboratory.KamaleldinIbrahimIsmail501/10/2002UncertaintyinMeasurementAsaresult,aproperestimateofuncertaintyadvisesthelaboratory,andinparticularitsclients,howmuchagreementmightreasonablybeexpectedbetweendifferentlaboratoriesmakingthesamemeasurement.KamaleldinIbrahimIsmai

5、l601/10/2002UncertaintyinMeasurementStandarduncertaintyofameasurementisdefinedbyISOasthestandarddeviation,i.e.approximately68%confidenceintervalforGaussiandata.KamaleldinIbrahimIsmail701/10/2002UncertaintyinMeasurementCOVERAGEFACTORS•Thestandarduncertaintyisthestandarddeviation

6、.•Foranormaldistributiononestandarddeviationrepresentsa68%confidenceintervalapproximately.•A95%,oroccasionallya99%,confidenceintervalisnormallywhatisquotedforanuncertainty.•ThisisderivedbymultiplicationofthestandarduncertaintybyaCOVERAGEFACTOR.KamaleldinIbrahimIsmail801/10/200

7、2UncertaintyinMeasurementCOVERAGEFACTORSTheprecisevalueofthecoveragefactorneededdependsonthenumberofmeasurementsmade,(actuallythenumberofdegreesofstatisticalfreedom).Foralarge(infinite)numberofmeasurements:95%ConfidenceisrepresentedbytheS.D.X1.9699%ConfidenceisrepresentedbyS.D.

8、X2.58KamaleldinIbrahimIsmail901/10/2002UncertaintyinMe