reliability and validity what's the difference信度和效度的区别是什么

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1、ReliabilityandValidity:What'stheDifference?ReliabilityDefinition:Reliabilityistheconsistencyofyourmeasurement,orthedegreetowhichaninstrumentmeasuresthesamewayeachtimeitisusedunderthesameconditionwiththesamesubjects.Inshort,itistherepeatabilityofyourmeasurement.Ameasureiscons

2、ideredreliableifaperson'sscoreonthesametestgiventwiceissimilar.Itisimportanttorememberthatreliabilityisnotmeasured,itisestimated.Therearetwowaysthatreliabilityisusuallyestimated:test/retestandinternalconsistency.Test/RetestTest/retestisthemoreconservativemethodtoestimatereli

3、ability.Simplyput,theideabehindtest/retestisthatyoushouldgetthesamescoreontest1asyoudoontest2.Thethreemaincomponentstothismethodareasfollows:1.)implementyourmeasurementinstrumentattwoseparatetimesforeachsubject;2).computethecorrelationbetweenthetwoseparatemeasurements;and3)a

4、ssumethereisnochangeintheunderlyingcondition(ortraityouaretryingtomeasure)betweentest1andtest2.InternalConsistencyInternalconsistencyestimatesreliabilitybygroupingquestionsinaquestionnairethatmeasurethesameconcept.Forexample,youcouldwritetwosetsofthreequestionsthatmeasurethe

5、sameconcept(sayclassparticipation)andaftercollectingtheresponses,runacorrelationbetweenthosetwogroupsofthreequestionstodetermineifyourinstrumentisreliablymeasuringthatconcept.OnecommonwayofcomputingcorrelationvaluesamongthequestionsonyourinstrumentsisbyusingCronbach'sAlpha.I

6、nshort,Cronbach'salphasplitsallthequestionsonyourinstrumenteverypossiblewayandcomputescorrelationvaluesforthemall(weuseacomputerprogramforthispart).Intheend,yourcomputeroutputgeneratesonenumberforCronbach'salpha-andjustlikeacorrelationcoefficient,thecloseritistoone,thehigher

7、thereliabilityestimateofyourinstrument.Cronbach'salphaisalessconservativeestimateofreliabilitythantest/retest.Theprimarydifferencebetweentest/retestandinternalconsistencyestimatesofreliabilityisthattest/retestinvolvestwoadministrationsofthemeasurementinstrument,whereastheint

8、ernalconsistencymethodinvolvesonlyoneadministrationofthatinstrument.Validit