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1、StatisticsforManagers UsingMicrosoft®Excel 5thEditionChapter7SamplingandSamplingDistributions1LearningObjectivesInthischapter,youwilllearn:TodistinguishbetweendifferentsurveysamplingmethodsTheconceptofthesamplingdistributionTocomputeprobabilitiesrelated
2、tothesamplemeanandthesampleproportionTheimportanceoftheCentralLimitTheorem2WhySample?Selectingasampleislesstime-consumingthanselectingeveryiteminthepopulation(census).Selectingasampleislesscostlythanselectingeveryiteminthepopulation.Ananalysisofasamplei
3、slesscumbersomeandmorepracticalthanananalysisoftheentirepopulation.3TypesofSamplesQuotaSamplesNon-ProbabilitySamplesJudgmentChunkProbabilitySamplesSimpleRandomSystematicStratifiedClusterConvenience4TypesofSamplesInanonprobabilitysample,itemsincludedarec
4、hosenwithoutregardtotheirprobabilityofoccurrence.Inconveniencesampling,itemsareselectedbasedonlyonthefactthattheyareeasy,inexpensive,orconvenienttosample.Inajudgmentsample,yougettheopinionsofpre-selectedexpertsinthesubjectmatter.5TypesofSamplesInaprobab
5、ilitysample,itemsinthesamplearechosenonthebasisofknownprobabilities.ProbabilitySamplesSimpleRandomSystematicStratifiedCluster6SimpleRandomSamplingEveryindividualoritemfromtheframehasanequalchanceofbeingselectedSelectionmaybewithreplacement(selectedindiv
6、idualisreturnedtoframeforpossiblereselection)orwithoutreplacement(selectedindividualisn’treturnedtotheframe).Samplesobtainedfromtableofrandomnumbersorcomputerrandomnumbergenerators.7SystematicSamplingDecideonsamplesize:nDivideframeofNindividualsintogrou
7、psofkindividuals:k=N/nRandomlyselectoneindividualfromthe1stgroupSelecteverykthindividualthereafterForexample,supposeyouweresamplingn=9individualsfromapopulationofN=72.So,thepopulationwouldbedividedintok=72/9=8groups.Randomlyselectamemberfromgroup1,sayin
8、dividual3.Then,selectevery8thindividualthereafter(i.e.3,11,19,27,35,43,51,59,67)8StratifiedSamplingDividepopulationintotwoormoresubgroups(calledstrata)accordingtosomecommoncharacteristic.Asimplerandomsampleisselectedfromeachsubgr
