总体特征抽样调查的设计与分析ppt课件.ppt

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1、CHAPTER-6SamplingerrorandconfidenceintervalspopulationsamplestatisticParametererrorSection1samplingerrorofmeanSection2tdistributionSection3confidenceintervalsforthepopulationmeanSection1samplingerrorofmeanAsimplerandomsampleisasampleofsizendrawnfromapo

2、pulationofsizeNinsuchawaythateverypossiblerandomsamplesnhasthesameprobabilityofbeingselected.Variabilityamongthesimplerandomsamplesdrawnfromthesamepopulationiscalledsamplingvariability,andtheprobabilitydistributionthatcharacterizessomeaspectofthesampling

3、variability,usuallythemeanbutnotalways,iscalledasamplingdistribution.Thesesamplingdistributionsallowustomakeobjectivestatementsaboutpopulationparameterswithoutmeasuringeveryobjectinthepopulation.[Example1]ThepopulationmeanofDBPintheChineseadultmenis72mmH

4、gwithstandarddeviation5mmHg.10adultparticipantswaschosenrandomlyfromtheChineseadultmen,herewecancalculatethesamplemeanandsamplestandarddeviation.Supposingsampling100times,what’stheresult?linkageNIfrandomsamplesarerepeatedlydrawnfromapopulationwithameanμa

5、ndstandarddeviationσ,wecanfind:1thesamplemeansaredifferentfromtheothers2Thesamplemeanarenotnecessaryequaltopopulationmeanμ3ThedistributionofsamplemeanissymmetricaboutμHOWTOEXPLORETHESAMPLINGDISTRIBUTIONFORTHEMEAN?Thedifferencebetweensamplestatisticsandpo

6、pulationparameterorthedifferenceamongsamplestatisticsarecalledsamplingerror.Inreallifewesampleonlyonce,butwerealizethatoursamplecomesfromatheoreticalsamplingdistributionofallpossiblesamplesofaparticularsize.Thesamplingdistributionconceptprovidesalinkbetw

7、eensamplingvariabilityandprobability.Choosingarandomsampleisachanceoperationandgeneratingthesamplingdistributionconsistsofmanyrepetitionsofthischanceoperation.Whensamplingfromanormallydistributedpopulationwithmeanμ,thedistributionofthesamplemeanwillbenor

8、malwithmeanμCentrallimitTheorem=50=10XPopulationdistributionn=4SamplingdistributionXn=16Whensamplingfromanonnormallydistributedpopulationwithmeanμ,thedistributionofthesamplemeanwillbeapproximatelynormalwithmeanμaslongasn