欢迎来到天天文库
浏览记录
ID:7703855
大小:391.52 KB
页数:18页
时间:2018-02-23
《propensity score matching》由会员上传分享,免费在线阅读,更多相关内容在工程资料-天天文库。
1、4.PropensityScoreMatchingSummaryPropensityscorematching(PSM)constructsastatisticalcomparisongroupthatisbasedonamodeloftheprobabilityofparticipatinginthetreatment,usingobservedcharacteristics.Participantsarethenmatchedonthebasisofthisprobability,orpro-pensityscore
2、,tononparticipants.Theaveragetreatmenteffectoftheprogramisthencalculatedasthemeandifferenceinoutcomesacrossthesetwogroups.ThevalidityofPSMdependsontwoconditions:(a)conditionalindependence(namely,thatunob-servedfactorsdonotaffectparticipation)and(b)sizablecommonsu
3、pportoroverlapinpropensityscoresacrosstheparticipantandnonparticipantsamples.Differentapproachesareusedtomatchparticipantsandnonparticipantsonthebasisofthepropensityscore.Theyincludenearest-neighbor(NN)matching,caliperandradiusmatching,stratificationandintervalmat
4、ching,andkernelmatchingandlocallin-earmatching(LLM).Regression-basedmethodsonthesampleofparticipantsandnon-participants,usingthepropensityscoreasweights,canleadtomoreefficientestimates.Onitsown,PSMisausefulapproachwhenonlyobservedcharacteristicsarebelievedtoaffect
5、programparticipation.Whetherthisbeliefisactuallythecasedependsontheuniquefeaturesoftheprogramitself,intermsoftargetingaswellasindividualtakeupoftheprogram.Assumingselectiononobservedcharacteristicsissufficientlystrongtodetermineprogramparticipation,baselinedataona
6、widerangeofpreprogramcharacteristicswillallowtheprobabilityofparticipationbasedonobservedcharacteristicstobespecifiedmoreprecisely.Sometestscanbeconductedtoassessthedegreeofselectionbiasorparticipationonunobservedcharacteristics.LearningObjectivesAftercompletingth
7、ischapter,thereaderwillbeabletodiscuss■CalculationofthepropensityscoreandunderlyingassumptionsneededtoapplyPSM■Differentmethodsformatchingparticipantsandnonparticipantsintheareaofcommonsupport■DrawbacksofPSMandmethodstoassessthedegreeofselectionbiasonunob-servedc
8、haracteristics■UseofPSMinregression-basedmethods53HandbookonImpactEvaluationPSMandItsPracticalUsesGivenconcernswiththeimplementationofrandomizedevaluations,the
此文档下载收益归作者所有