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页数:27页
时间:2019-05-25
《class13 Regression Analysis of Correlated Data-new-f2008》由会员上传分享,免费在线阅读,更多相关内容在行业资料-天天文库。
1、TheRegressionAnalysisofCorrelatedDataTherearemanysituationsthatresultinsamplesthatarenotmadeupofindependentobservations•Familydata:Wecanexpectthatsubjectsinthesamefamilywillhaveobservationsthataremorealikewhencomparedtoeachotherthanwhencomparedtosubjectsinotherfamilies.•Datacollecte
2、dusingnon-randomsampling:Whenusingasamplingschemethatselectsseveralhospitalsfromwhichsubjectswillberecruited,subjectsatthesamehospitalwillshareunmeasuredcharacteristicsthatwouldnothappenifsubjectswereselectedrandomlyfromthegeneralpopulation.•Repeatedmeasures:Whentakingrepeatedmeasur
3、ementsfromsubjects,observationsthatarefromthesamesubjectwilltendtobemorealikethanwhencomparedtoothersubjectsobservations.Repeatedobservationscloserintimefromthesamesubjectmayalsobemorealikethanthosefurtherapartintime.2ConsequencesofNon-IndependentDataConsiderthisexperiment:•Youatten
4、daconventionforidenticaltripletsthathas1,000setsofidenticaltriplets.•Youdecideyouhavetimetotake1,000systolicbloodpressuremeasurements.Youcaneither:1.Collectbloodpressuresfromallmembersof333-1/3setsoftripletsor,2.Takeonemeasurefromeachofthe1,000sets.IfyouwantaproperestimateofSBPatthe
5、convention,areyoubetteroffdoing1or2?•Ifmembersofatriplettendtohavesimilarbloodpressures,yougetlittleadditionalinformationbymeasuringmorethanonememberofasibship.•Thetotalinformationcontentofyourdatawillbereducedifyoudon’thaveindependentobservations.•Thestandarderrorsonyourestimateswi
6、llbetoosmallifyoudon’taccountforthecorrelations–yourdataisnotasgoodasyouthink!3Situation#2:SleepHoursinMenandWomen•Youaretestingthehypothesisthatmothersandfathersofnewbornswillgetsignificantlydifferenthoursofsleep,whereyoubelievethatmenwillsleepmorethanwomen.•Youcandothestudytwoways
7、:1.Youcollect50couplesandcalculatethedifferenceinsleephoursbetweenthemotherandfatherofanewborn.Isthisdifferencesignificantlydifferentfromzero?[pairedt-testwith50pairs].2.Youaccumulate50mothersand50fathersofnewborns,withnoattempttorecruitcouples.Youthencalculatethemeannumberofhoursof
8、sleepinmothersandin
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