Basic-statisticsPPT课件下载推荐.ppt
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Basic-statisticsPPT课件下载推荐.ppt
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Itsadvantageistoallowthereseachertomakedecisionsaboutthepopulationwithoutstudyingtheentirepopulation.,1.2,Twoterms,parameter,statistic,Parameterisadescriptivemeasureofthepopulation,whichisdenotedbyGreekletterssuchasPage180.e.g:
populationmeanpopulationvariancepopulationstandarddeviation,Parameter,Statisticisadescriptivemeasureofasample,whichisdenotedbyaRomanletter,suchastheexamplesinpage180e.g.samplemeansamplevariancesamplestandarizationdeviation,Statistic,Diferentiationbetweenparameterandstatisticisimportantonlyintheuseofinferentialstatistics.Thestatisticianoftenwantstoestimatethevalueofaparameter.However,therearesomefactorscanaffectthevalues,especially:
Note,time,money,Anexample:
SupposeyouareanEnglishteacheratNanjingUniversityandyouwanttoknowtherelationshipbetweentheuseofstrategiesandtheEnglishproficiencyofalltheNanjingUniversitystudents.Therearemorethan10,000studentsontwocampuses.Obviously,youcannnotaffordthemoneyandtimetotakeacensus.Whatyoumaydoistosurvey400studentsasasamplebyaquestionnaire.Then,howdowedo?
descriptivestatisticsinferentialstatistics,Youusedescriptivestatisticstogettoknowwhichstrategiesaremorefrequentlyusedbythese400students.Theresultsyouhavegotareonsample.YoumayuseinferentialstatisticstoexaminetherelationbewteentheuseofstrategiesandEnglishachievement,ortoseewhetherthemalestudentsdifferfromthefemalestudentsintheiruseofstategiesbasedonthenotionprobability,Descriptiveanalysisorstatisticsdescribesthegeneralpatternortendencyemergingfromthedatacollected.Inferentialanalysisorstatistics,morecomplicatedthandescriptive,aimsatpredictionsbeyondthesampledata.,Conclusion,Frequencies,Thesimplestwaytoorganizethedataistodescribetheirfrequencydistributionwhichcanreduceandsummarizedataeffectivelyandefficiently.,frequencydistribution,bargraph,polygon,piechart,Ifthetotalpossiblevaluesareverylimited.,forexample:
ifthestudentsresponsestoquestionnaireitemsarenomorethanfive:
1,2,3,4,5,frequencydistributioncanbeobtainedsimplybytallyingupalltheresponses,asshownintable1.,Table1:
Frequencydistribution,Ifthetotalpossiblevaluesarevarious,suchaspeoplesageandstudentstestscores,weneedtogrouptherawdataintoclasses.,Inthiscase,thefrequencydistributionisconcernedwithclassesratherthanwitheachindividualscore.Howdowedescribethefrequencydistributionintermsofclasses?
Therearenohard-and-fastrulestofollow.,Generallyspeaking,wemayconstructthefrequencydistributionofthesedatainthreesteps:
1.Determinetherangeoftherawdata,2.Determinethenumberoftheclasses,3.Determinethewidthoftheclassinterval,58,65,84,70,90,75,86,76,80,82,83,84,69,84,85,86,72,89,75,92,Attention,1.Therangeoftherawdata:
definedasthedifferencebetweenthelargestandsmallestnumbers.,2.Thenumberofclasses,toomany:
cannotachievegeneralizationtoofew:
cannotseetheimportantdifferences,theappropriatenumberofclasses,between5and10,92-58=34,Attention,range3.thewidthoftheclassinterval=thenumberofclasses组距=全距/组数,Asusual,itis5,10,15andsoon.,4.Thefrequencydistributionmustincludeallthedatagiven.Therefore,thefrequencydistributionshouldstart:
atavalueequaltoorlowerthanthelowestnumberoftheungroupeddataend:
atavalueequaltoorhigherthanthehighestnumber.,Table2:
Frequencydistributionintermsoffiveclasses,Table3:
Frequencydistributionintermsofthreeclasses,Ifyouwanttoknowtherelativestandingofanyparticularscoreinagroupofscores,youcanshowitbyapercentilescore.,formula:
CumulativeFPercentile=(100)N,1.Cumulativefrequency(F):
referstothefrequencyofthescoreorthescoreswithintheclassjustbelow.2.N:
representsthetotalnumbelofscores.3.Percentile:
definedasanumberwhichrepresentsthepercentofscoresthataparticularrawscoreexceeds.,Table4:
Frequencydistributionwithcumulativefrequenciesandpercenta
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