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1、计量经济学导论第四版答案中文版【篇一：计量经济学导论(伍德里奇第三版)课后习题答案chapter1】>solutionstoproblems1.1(i)ideally,wecouldrandomlyassignstudentstoclassesofdifferentsizes.thatis,eachstudentisassignedadifferentclasssizewithoutregardtoanystudentcharacteristicssuchasabilityandfamilyback
2、ground.forreasonswewillseeinchapter2,wewouldlikesubstantialvariationinclasssizes(subject,ofcourse,toethicalconsiderationsandresourceconstraints).(ii)anegativecorrelationmeansthatlargerclasssizeisassociatedwithlowerperformance.wemightfindanegativecorrel
3、ationbecauselargerclasssizeactuallyhurtsperformance.however,withobservationaldata,thereareotherreasonswemightfindanegativerelationship.forexample,childrenfrommoreaffluentfamiliesmightbemorelikelytoattendschoolswithsmallerclasssizes,andaffluentchildreng
4、enerallyscorebetteronstandardizedtests.anotherpossibilityisthat,withinaschool,aprincipalmightassignthebetterstudentstosmallerclasses.or,someparentsmightinsisttheirchildrenareinthesmallerclasses,andthesesameparentstendtobemoreinvolvedintheirchildren’sed
5、ucation.(iii)giventhepotentialforconfoundingfactors–someofwhicharelistedin(ii)–findinganegativecorrelationwouldnotbestrongevidencethatsmallerclasssizesactuallyleadtobetterperformance.somewayofcontrollingfortheconfoundingfactorsisneeded,andthisisthesubj
6、ectofmultipleregressionanalysis.1.2(i)hereisonewaytoposethequestion:iftwofirms,sayaandb,areidenticalinallrespectsexceptthatfirmasuppliesjobtrainingonehourperworkermorethanfirmb,byhowmuchwouldfirma’soutputdifferfromfirmb’s?(ii)firmsarelikelytochoosejobt
7、rainingdependingonthecharacteristicsofworkers.someobservedcharacteristicsareyearsofschooling,yearsintheworkforce,andexperienceinaparticularjob.firmsmightevendiscriminatebasedonage,gender,orrace.perhapsfirmschoosetooffertrainingtomoreorlessableworkers,w
8、here―ability‖mightbedifficulttoquantifybutwhereamanagerhassomeideaabouttherelativeabilitiesofdifferentemployees.moreover,differentkindsofworkersmightbeattractedtofirmsthatoffermorejobtrainingonaverage,andthismightnotbeevidenttoemployers
