《抽样与估计》PPT课件

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1、4-1Chapter4:SamplingandEstimation4-2NeedforSamplingVerylargepopulationsDestructivetestingContinuousproductionprocessTheobjectiveofsamplingistodrawavalidinferenceaboutapopulation.4-3SampleDesignSamplingPlan–adescriptionoftheapproachthatwillbeusedtoobtainsamplesfromapopulationObjectives（总体中重要的参数估

2、计、或总体之间是否存在显著差异）TargetpopulationPopulationframe（目标总体完整的名单）MethodofsamplingOperationalproceduresfordatacollectionStatisticaltoolsforanalysis4-4SamplingMethodsSubjectiveJudgmentsamplingConveniencesampling（易获得性）ProbabilisticSimplerandomsampling–everysubsetofagivensizehasanequalchanceofbeingselecte

3、d4-5PHStatToolRandomSampleGeneratorPHStatmenu>Sampling>RandomSampleGeneratorEntersamplesizeSelectsamplingmethod4-6ExcelDataAnalysisToolSamplingExcelmenu>Tools>DataAnalysis>SamplingSpecifyinputrangeofdataChoosesamplingmethodSelectoutputoption4-7OtherSamplingMethodsSystematicsamplingStratifieds

4、amplingClustersamplingSamplingfromacontinuousprocess4-8ErrorsinSamplingNonsamplingerrorPoorsampledesignSampling(statistical)errorDependsonsamplesizeTradeoffbetweencostofsamplingandaccuracyofestimatesobtainedbysampling4-9EstimationEstimation–assessingthevalueofapopulationparameterusingsampledata

5、.Pointestimate–asinglenumberusedtoestimateapopulationparameterConfidenceintervals–arangeofvaluesbetweenwhichapopulationparameterisbelievedtobealongwiththeprobabilitythattheintervalcorrectlyestimatesthetruepopulationparameter4-10CommonPointEstimateŝ4-11Example4-12TheoreticalIssuesUnbiasedestima

6、tor–oneforwhichtheexpectedvalueequalsthepopulationparameteritisintendedtoestimateThesamplevarianceisanunbiasedestimatorforthepopulationvariance4-13IntervalEstimatesRangewithinwhichwebelievethetruepopulationparameterfallsExample:Galluppoll–percentageofvotersfavoringacandidateis56%witha3%marginof

7、error.Intervalestimateis[53%,59%]4-14ConfidenceIntervalsConfidenceinterval(CI)–anintervalestimatedthatspecifiesthelikelihoodthattheintervalcontainsthetruepopulationparameterLevelofconfidence(1–a)–theprobabilitythattheCIcontainsthe