poster 0764-2017: multiple-group calibration in sas ...0 10 20 30 40 50 60 0 1 . -0 5 0 . -0 0.00...
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Multiple-GroupCalibrationinSAS®:PROCIRTandSAS/IML®
SASandallotherSASInstituteInc.productorservicenamesareregisteredtrademarksortrademarksofSASInstituteInc.intheUSAandothercountries.®indicatesUSAregistration.Otherbrandandproductnamesaretrademarksoftheirrespectivecompanies.
Multiple-GroupCalibrationinSAS®:PROCIRTandSAS/IML®Kyungyong Kim1,Seohee Park1,Jinah Choi1,andHongwook Seo2
1UniversityofIowaand2ACT
ABSTRACT• Itemresponsetheory(IRT)hasbeengainingpopularityinthefieldofeducationalandpsychologicalmeasurement.• IRTassumesthattheprobabilityofacorrectresponsetoanitemisafunctionofpersonanditemparameters.• InIRT,manyapplicationsrequireacommonabilityscale.However,theoriginandunitofmeasurementoftheability
scaleareundetermined.• IRTestimationprogramstypicallychoosetheabilityscalesothatmeanandSDofthepersonparametersare0and
1forthegroupathand.• Whenestimatingparametersfortwodifferenttestformswithnonequivalentgroups,thiscommonprocedureyields
parameterestimatesthatareontwodifferentabilityscales.• Multiple-groupcalibration,whichissupportedbytheIRTprocedureinSAS/STAT®(SASInstituteInc.,2013),isone
approachthatisoftenusedtohandlethisissue.• Toconductmultiple-groupcalibration,thetwotestformsmustsharesomecommonitems.• ThepurposeofthispaperistocomparetheperformanceofPROCIRT,amultiple-groupcalibrationprogramwritten
usingSAS/IML®,andacommercialsoftwareflexMIRT®(Cai,2013)intermsoftherecoveryofitemparameters.
METHODS• AsimulationstudywasconductedtocomparetheperformanceofPROCIRT,SAS/IML®,andflexMIRT®usingthe
twoparameterlogistic(2PL)model(Birnbaum,1968):𝑃"# 𝜃" 𝑎#, 𝑏# = 1/(1 + exp[1.7𝑎#(𝜃" − 𝑏#)]),
where𝑎# and𝑏# arethediscriminationanddifficultyparametersforitem𝑗,and𝜃" istheabilityparameterforperson𝑖.
• Thestudyfactorsforthesimulationstudywereasfollows:
• Therecoveryoftheitemparameterswereevaluatedusingthreestatistics:bias,standarderror(SE),androotmeansquarederror(RMSE).
RESULTS
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Par. ProgramFormY Form X
Bias SE RMSE Bias SE RMSE
𝑎SAS®PROCIRT .027 .047 .055 .026 .045 .053
SAS/IML® .002 .048 .048 .000 .048 .048flexMIRT® -.012 .047 .049 -.016 .047 .050
𝑏SAS®PROCIRT -.225 .046 .232 -.260 .045 .266
SAS/IML® -.005 .050 .050 -.007 .051 .051flexMIRT® .009 .049 .052 .007 .050 .054
StudyFactor FormY/Group1(Reference) FormX/Group2
TestLength 40unique items+20commonitems 40unique items+20commonitems
Sample Size 3,000 3,000
AbilityDistribution N(0, 1) N(0.5,1)
Program SAS® PROCIRT SAS/IML® flexMIRT®
EstimationMethod MarginalMLE MarginalMLE Marginal MLENumericalIntegration Adaptive Gauss-Hermite Compositemidpoint Compositemidpoint
AbilityDistribution (BothGroups) Normal Empirical EmpiricalOptimizationMethod Quasi-Newton Newton-Raphson Newton-Raphson
Table1.Programcomparison
Note:ForSAS/IML®andflexMIRT®,thedistributionsofabilityforbothgroupsareestimatedempiricallywithoutassuminganyshapes.
Table2.Simulationresults
• Overall,thevaluesofbiasfortheitemparameterestimatesobtainedwithSAS®PROCIRTtendedtobelargerthanthoseobtainedwithSAS/IML®andflexMIRT®.
• Thistendencywasmorenoticeableforthe𝑏-parametersthanthe𝑎-parameters.• Asaresult,SAS®PROCIRTyieldeditemparameterestimateswiththelargestvaluesofRMSE.• ItemparameterestimatesobtainedwithSAS/IML®andflexMIRT®werecomparableintermsofallthreeevaluation
criteria.
RESULTSCONTINUED CONCLUSIONS/LIMITATIONS
REFERENCES
SASandallotherSASInstituteInc.productorservicenamesareregisteredtrademarksortrademarksofSASInstituteInc.intheUSAandothercountries.®indicatesUSAregistration.Otherbrandandproductnamesaretrademarksoftheirrespectivecompanies.
Multiple-GroupCalibrationinSAS®:PROCIRTandSAS/IML®Kyungyong Kim1,Seohee Park1,Jinah Choi1,andHongwook Seo2
1UniversityofIowaand2ACT
• TheperformanceofSAS/IML®andflexMIRT areverysimilarintermsoftherecoveryof𝑎-parameters.• SAS®PROCIRTyieldsinaccurate𝑏-parameterestimates.
è Formultiple-groupcalibration,themaindifferencebetweenSAS®PROCIRTandtheothertwoprogramsisthespecificationoftheabilitydistributionsduringtheestimationprocess.SAS®PROCIRTassumesabilitiesforbothgroupsfollowanormaldistribution,whereasSAS/IML®andflexMIRT®estimatetheabilitydistributionsconcurrentlywiththeitemparameters.
• SAS®PROCIRTrequiressignificantlymorecomputationtimethantheothertwoprograms.
Note:TheSAS/IML®programwrittenforthisstudyonlyprovidestheitemparameterestimatesasthefinaloutput.• InmostIRTestimationprograms,priordistributionscanbeassumedfortheitemparameterstoguarantee
convergence(i.e.,marginalizedBayesianestimation;Mislevy,1986).However,SAS®PROCIRTonlysupportsthemarginalmaximumlikelihoodestimationmethod(BockandAitkin,1981).
• Becauseofthesmallnumberofconditionsexaminedinthesimulationstudy,thisstudyislimitedinitsabilitytogeneralizethefindingstomeasurementconditionsthatarenotincludedinthesimulationstudy.
Birnbaum,A.(1968).Estimationofanability.InF.M.Lord&M.R.Novick (Eds.),Statisticaltheoriesofmentaltestscores(pp.423-479).Reading,MA:Addison-Wesley.Bock,R.D.,&Aitkin,M.(1981).Marginalmaximumlikelihoodestimationofitemparameters:ApplicationofanEMalgorithm.Psychometrika,46,443-459.Cai,L.(2017).flexMIRT®version3.51:Flexiblemultilevelmultidimensionalitemanalysisandtestscoring[Computersoftware].ChapelHill,NC:VectorPsychometricGroup.Mislevy,R.J. (1986).Bayesmodelestimationinitemresponsemodels.Psychometrika,51,177-195.SASInstituteInc.(2013).SAS/STAT®13.1User’sGuide:TheIRTprocedure[Computersoftware].Cary,NC.
ContactInformation:[email protected]
Figure1.Conditionalbias,SE,andRMSEvaluesforthe𝒂- and𝒃-parameters.Note:Inallfigures,theresultsforSAS®PROCIRTaredepictedwithorange,theresultsforSAS/IML® aredepictedwithgreen,andtheresultsforflexMIRT aredepictedwithred.
• SAS®PROCIRTsystematicallyoverestimatesthe𝑎-parametersandunderestimatesthe𝑏-parametersforallitemsinFormsXandY.
• Betweenthetwoitemparameters,SAS®PROCIRTproducedsignificantlylessaccurate𝑏-parameterestimatesintermsofboththeconditionalbiasandRMSEstatistics.
• SAS/IML®andflexMIRT yieldednearlyunbiasedestimatesforboththe𝑎- and𝑏-parameters.
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Program SAS®PROCIRT SAS/IML® flexMIRT
ComputationTime 3minutes 0.75seconds 0.84seconds
SASandallotherSASInstituteInc.productorservicenamesareregisteredtrademarksortrademarksofSASInstituteInc.intheUSAandothercountries.®indicatesUSAregistration.Otherbrandandproductnamesaretrademarksoftheirrespectivecompanies.