商务统计学最新英文版教学课件第8章.ppt

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1、ConfidenceIntervalEstimationChapter8ObjectivesInthischapter,youlearn:ToconstructandinterpretconfidenceintervalestimatesforthepopulationmeanandthepopulationproportionTodeterminethesamplesizenecessarytodevelopaconfidenceintervalforthepopulationmeanorpopul

2、ationproportionChapterOutlineContentofthischapterConfidenceIntervalsforthePopulationMean,μwhenPopulationStandardDeviationσisKnownwhenPopulationStandardDeviationσisUnknownConfidenceIntervalsforthePopulationProportion,πDeterminingtheRequiredSampleSizePoin

3、tandIntervalEstimatesApointestimateisasinglenumber,aconfidenceintervalprovidesadditionalinformationaboutthevariabilityoftheestimatePointEstimateLowerConfidenceLimitUpperConfidenceLimitWidthofconfidenceintervalDCOVAWecanestimateaPopulationParameter…Point

4、EstimateswithaSampleStatistic(aPointEstimate)MeanProportionpπXμDCOVAConfidenceIntervalsHowmuchuncertaintyisassociatedwithapointestimateofapopulationparameter?AnintervalestimateprovidesmoreinformationaboutapopulationcharacteristicthandoesapointestimateS

5、uchintervalestimatesarecalledconfidenceintervalsDCOVAConfidenceIntervalEstimateAnintervalgivesarangeofvalues:TakesintoconsiderationvariationinsamplestatisticsfromsampletosampleBasedonobservationsfrom1sampleGivesinformationaboutclosenesstounknownpopulati

6、onparametersStatedintermsoflevelofconfidencee.g.95%confident,99%confidentCanneverbe100%confidentDCOVAConfidenceIntervalExampleCerealfillexamplePopulationhasµ=368andσ=15.Ifyoutakeasampleofsizen=25youknow368±1.96*15/=(362.12,373.88).95%oftheintervalsforme

7、dinthismannerwillcontainµ.Whenyoudon’tknowµ,youuseXtoestimateµIfX=362.3theintervalis362.3±1.96*15/=(356.42,368.18)Since356.42≤µ≤368.18theintervalbasedonthissamplemakesacorrectstatementaboutµ.Butwhatabouttheintervalsfromotherpossiblesamplesofsize25?DCOVA

8、ConfidenceIntervalExample(continued)Sample#XLowerLimitUpperLimitContainµ?1362.30356.42368.18Yes2369.50363.62375.38Yes3360.00354.12365.88No4362.12356.24368.00Yes5373.88368.00379.76YesDCOVAConfidenceIntervalExampleInpracticeyouonly