抽样技术课件

抽樣技術

SamplingTechnology一、基本抽樣問題基本概念制定抽樣計畫的步驟抽樣誤差與非抽樣誤差概率抽樣方法非概率抽樣方法本節概要（1）Tounderstandtheconceptofsampling.Tolearnthestepsindevelopingasamplingplan.Tounderstandthedifferencesbetweenprobabilitysamplesandnonprobabilitysamples.Tounderstandtheconceptsofsamplingerrorandnonsamplingerror.本節概要（2）Toreviewthetypesofprobabilitysamplingmethods.Togaininsightintononprobabilitysamplingmethods.基本概念Population（總體）Thetotalgroupofpeoplefromwhominformationisneeded.Census（普查）Dataobtainedfromorabouteverymemberofthepopulationofinterest.Sample（樣本）Asubsetofthepopulationofinterest.StepsinDevelopingaSamplePlan

設計一個抽樣方案的步驟Step1:DefinethePopulationofInterestStep2:ChooseDataCollectionMethodStep3:ChooseSamplingFramesStep4:SelectaSamplingMethodStep5:DetermineSampleSizeStep6:DevelopandSpecifyOperationalPlanStep7:ExecuteOperationalSamplingPlanStepsinDevelopingaSamplingPlan

（1）Step1:DefiningthePopulationofInterestBasesfordefiningthepopulationofinterestinclude:GeographyDemographicsUseAwarenessStepsinDevelopingaSamplingPlan

（2）Step2:ChoosingaDataCollectionMethodTheselectionofadatacollectionmethodhasimplicationsforthesamplingprocess.Step3:ChoosingaSamplingFrameSamplingframeListofpopulationelementsfromwhichtoselectunitstobesampled.StepsinDevelopingaSamplingPlan

（3）Step4:SelectingtheSamplingMethodProbabilitysamplesSamplesinwhicheveryelementofthepopulationhasaknown,nonzeroprobabilityofselection.NonprobabilitysamplesIncludetheselectionofspecificelementsfromthepopulationinanonrandommanner.StepsinDevelopingaSamplingPlan

（4）Step4:SelectingtheSamplingMethod(continued)Samplingerror:Thedifferencebetweenthesamplevalueandthetruevalueofthepopulationmean.StepsinDevelopingaSamplingPlan

（5）AdvantagesofprobabilitysamplesDisadvantagesofprobabilitysamples-Theresearchercanbesureofobtaininginformationfromarepresentativecrosssectionofthepopulationofinterest.-Samplingerrorcanbecomputed.-Thesurveyresultsareprojectable

tothetotalpopulation.-Theyaremoreexpensivethan

nonprobabilitysamplesofthesamplesizeinmostcases.Therulesforselectionincreaseinterviewingcostsandprofessionaltimemustbespentindevelopingthesampledesign.-Probabilitysamplestakemoretimetodesignandexecutethannon-probabilitysamples.StepsinDevelopingaSamplingPlan

（6）AdvantagesofnonprobabilitysamplesDisadvantagesofnonprobabilitysamples-Nonprobabilitysamplescostlessthanprobabilitysamples.Thischaracteristicofnonprobability

samplesmayhaveconsiderableappealinthosesituationswhereaccuracyisnotofcriticalimportance.-Nonprobabilitysamplesordinarilycanbeconductedmorequicklythanprobabilitysamples.

-Samplingerrorcannotbecomputed.-Theresearcherdoesnotknowthedegreetowhichthesampleisrepresentativeofthepopulationfromwhichitwasdrawn.-Theresultsofnonprobability

samplescannotandshouldnotbeprojectedtothetotalpopulation.StepsinDevelopingaSamplingPlan

（7）Step5:DetermineSampleSizeOncethesamplingmethodhasbeenchosen,thenextstepistodeterminetheappropriatesamplesize.Step6:DevelopingOperationalProceduresforSelectingSampleElementsInvolvesdeterminingwhetheraprobabilityornonprobabilitysampleisbeingused.StepsinDevelopingaSamplingPlan

（8）Step7:ExecutionoftheSamplingPlanThefinalstepinthesamplingprocessinvolvesexecutionoftheoperationalsamplingplandiscussedintheprevioussteps.Itisimportantthatthisstepincludeadequatecheckingtomakesurethatspecifiedproceduresareadheredto.ClassificationofSamplingMethods

抽樣方法分類SamplingMethodsProbabilitySamplesSimpleRandomClusterSystematicStratifiedNon-probabilityQuotaJudgmentConvenienceSnowballProbabilitySamplingMethods

概率抽樣SimpleRandomSampling（簡單隨機抽樣）Isconsideredtobethepurestformofprobabilitysampling.Aprobabilitysampleisasampleinwhicheveryelementofthepopulationhasaknownandequalprobabilityofbeingselectedintothesample.ProbabilityofSelection=SampleSizePopulationSizeProbabilitySamplingMethods

SystematicSampling（系統抽樣）Probabilitysamplinginwhichtheentirepopulationisnumbered,andelementsaredrawnusingaskipinterval.SkipInterval=PopulationSizeSampleSizeProbabilitySamplingMethods

StratifiedSamples（分層抽樣）Stratifiedsamplesareprobabilitysamplesthataredistinguishedbythefollowingproceduralsteps:First,theoriginalorparentpopulationisdividedintotwoormoremutuallyexclusiveandexhaustivesubsets(e.g.,maleandfemale).Second,simplerandomsamplesofelementsfromthetwoormoresubsetsarechosenindependentlyfromeachother.ProbabilitySamplingMethods

ClusterSamples（整群抽樣）Inthecaseofclustersamples,thesamplingunitsareselectedingroups.Therearetwobasicstepsinclustersampling:First,thepopulationofinterestisdividedintomutuallyexclusiveandexhaustivesubsets.Second,arandomsampleofthesubsetsisselected.NonprobabilitySamplingMethods

非概率抽樣方法ConvenienceSamples（便利樣本）Nonprobabilitysamplesusedprimarilybecausetheyareeasytocollect.JudgmentSamples（判斷樣本）Nonprobabilitysamplesinwhichtheselectioncriteriaarebasedonpersonaljudgmentthattheelementisrepresentativeofthepopulationunderstudy.NonprobabilitySamplingMethods

QuotaSamples（配額樣本）Nonprobabilitysamplesinwhichpopulationsubgroupsareclassifiedonthebasisofresearcherjudgment.SnowballSamples（滾雪球樣本）Nonprobabilitysamplesinwhichselectionofadditionalrespondentsisbasedonreferralsfromtheinitialrespondents.本節小結（1）Thepopulation,oruniverse,isthetotalgroupofpeopleinwhoseopinionsoneisinterested.Acensusinvolvescollectingdesiredinformationfromallthemembersofthepopulationofinterest.Asampleissimplyasubsetofapopulation.本節小結（2）Probabilitysamplingmethodsareselectedinsuchawaythateveryelementofthepopulationhasaknown,nonzeroprobabilityofselection.Nonprobabilitysamplingmethodsincludeallmethodsthatselectspecificelementsfromthepopulationinanonrandommanner.確定概率抽樣的樣本容量確定樣本容量的方法抽樣分佈二、確定樣本含量本節概要（1）Tolearnthefinancialandstatisticalissuesinthedeterminationofsamplesize.Todiscoverthemethodsfordeterminingsamplesize.Togainanappreciationofanormaldistribution.本節概要（2）Tounderstandpopulation,sample,andsamplingdistribution.Todistinguishbetweenpointandintervalestimates.Torecognizeproblemsinvolvingsamplingmeansandproportions.DeterminingSampleSizeforProbabilitySamples

確定概率抽樣的樣本容量Theprocessofdeterminingsamplesizeforprobabilitysamplesinvolvesfinancial,statistical,andmanagerialissues.Otherthingsbeingequal,thelargerthesample,thelessthesamplingerror.MethodsforDeterminingSampleSize

確定樣本容量的方法BudgetAvailable可支配預算RulesofThumb單憑經驗的做法NumberofSubgroupstobeAnalyzedOften,samplesizeforaprojectisdetermined,atleastindirectly,bythebudgetavailableAttimes,thesizeofasamplemayboildowntotheuseofsometypeofruleofthumborafeelSeriousconsiderationmustbegiventothenumberandanticipatedsizeofvarioussubgroupsofthetotalsampleTraditionalStatisticalMethods

傳統的統計方法Piecesofinformationrequiredtomakethenecessarycalculationswhenusingasampleresult:Thedesiredlevelofconfidencethatthesampleresultwillfallwithinacertainrange(resultplusorminussamplingerror)oftruepopulationvalueAnestimateofthepopulationstandarddeviation總體標準差估計Theacceptablelevelofsamplingerror抽樣的容許誤差水準TheNormalDistribution

正態分佈GeneralProperties(一般特徵)Thenormaldistributionisacontinuousdistributionthatisbellshapedandsymmetricalaboutthemean-mean,median,andmodeareequal.Sixty-eightpercentoftheobservationsfallwithinplusorminusonestandarddeviationofthemean,approximately95percentfallwithinplusorminustwostandarddeviations,andapproximately99.5percentfallwithinplusorminusthreestandarddeviations.TheNormalDistribution

為什麼要重視正態分佈？First,manyvariablesencounteredbymarketershaveprobabilitydistributionsthatareclosetothenormaldistribution.Second,thenormaldistributionisusefulforanumberoftheoreticalreasons;oneofthemoreimportantoftheserelatestothecentrallimittheorem.TheNormalDistribution

CentralLimitTheorem（中心極限定理）Adistributionofalargenumberofsamplemeansorsampleproportionswillapproximateanormaldistributionregardlessoftheactualdistributionofthepopulationfromwhichtheyweredrawn.StandardNormalDistributionAnormaldistributionwithameanofzeroandastandarddeviationofone.Population,Sample,andSamplingDistribution

總體、樣本與抽樣分佈

PopulationDistribution（總體分佈）Apopulationdistributionisafrequencydistributionofalloftheelementsofthepopulation.SampleDistribution（樣本分佈）Asampledistributionisafrequencydistributionofalltheelementsofthepopulation.Population,Sample,andSamplingDistribution

SamplingDistributionoftheSampleMean（樣本均數的抽樣分佈）Afrequencydistributionofthemeansofmanysamplesdrawnfromaparticularpopulation.Itisnormallydistributed.SamplingDistributionoftheMean

StandardDeviation（標準差）Ameasureofdispersioncalculatedbysubtractingthemeanofaseriesfromeachvalueintheseries,squaringeachresult,summingthem,dividingthesumbythenumberofitemsminus1,andtakingthesquarerootofthisvalue.StandardErroroftheMean

（均數標準誤）Thestandarddeviationofadistributionofsamplemeans.SamplingDistributionoftheMean

MakingInferenceontheBasisofaSingleSample（單樣本的簡單推斷）PointEstimates（點估計）Inferencesregardingthesamplingerrorassociatedwithaparticularestimateofapopulationvalue.IntervalEstimates（區間估計）Inferencesregardingthelikelihoodthatapopulationvaluewillfallwithinacertainrange.SamplingDistributionoftheMean

MakingInferenceontheBasisofaSingleSampleConfidenceLevel（置信水準）Theprobabilitythataparticularconfidenceintervalwillincludethetruepopulation.SamplingDistributionoftheProportion

比例的抽樣分佈GeneralProperties（一般特徵）Afrequencydistributionoftheproportionsofmanysamplesdrawnfromaparticularpopulation.Itisnormallydistributed.PreferencesMarketingresearchershaveatendencytopreferdealingwithsamplesizeproblemsasproblemsofestimatingproportionsratherthanmeans.SampleSizeDistributions

樣本容量的分佈

ProblemsInvolvingMeans（均數估計的問題）Thelevelofconfidence(Z)andtheamountoferror(E)tobeusedincalculatingtherequiredsamplesizemustbesetbytheresearcher.Indesigningasamplingprocedure,anacceptabletrade-offbetweenaccuracy,levelofconfidence,andcostmustbeevaluated.Thepopulationstandarddeviationmustbeestimated.SampleSizeDistributions

ProblemsInvolvingProportionsThelevelofconfidence(Z)andtheamountoferror(E)tobeusedincalculatingtherequiredsamplesizemustbesetbytheresearcher.AdvantagesInvolvingProportionsIfthereisnobasisforestimatingP,youcanmakewhatissometimesreferredtoasthemostpessimisticorworsecaseassumptionregardingthevalueofP.StatisticalPower

統計效能TypeIError（I型錯誤）Theerrorofconcludingthatthereisadifferencewhenthereisnotadifference.T