IBM_SPSS_Exact_Tests

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1、IBMSPSSExactTestsCyrusR.MehtaandNitinR.PatelNote:Beforeusingthisinformationandtheproductitsupports,readthegeneralinformationunderNoticesonpage213.ThiseditionappliestoIBM®SPSS®ExactTests20andtoallsubsequentreleasesandmodificationsuntilotherwiseindicatedinnew

2、editions.MicrosoftproductscreenshotsreproducedwithpermissionfromMicrosoftCorporation.LicensedMaterials-PropertyofIBM©CopyrightIBMCorp.1989,2011.U.S.GovernmentUsersRestrictedRights-Use,duplicationordisclosurerestrictedbyGSAADPScheduleContractwithIBMCorp.Pref

3、aceExactTests™isastatisticalpackageforanalyzingcontinuousorcategoricaldatabyexactmethods.ThegoalinExactTestsistoenableyoutomakereliableinferenceswhenyourdataaresmall,sparse,heavilytied,orunbalancedandthevalidityofthecorrespondinglargesampletheoryisindoubt.T

4、hisisachievedbycomputingexactpvaluesforaverywideclassofhypothesistests,includingone-,two-,andK-sampletests,testsforunorderedandorderedcategoricaldata,andtestsformeasuresofasso-ciation.Thestatisticalmethodologyunderlyingtheseexacttestsiswellestablishedinthes

5、tatisticalliteratureandmayberegardedasanaturalgeneralizationofFisher’sex-acttestforthesingle22×contingencytable.Itisfullyexplainedinthisusermanual.Therealchallengehasbeentomakethismethodologyoperationalthroughsoftwaredevelopment.Historically,thishasbeenadif

6、ficulttaskbecausethecomputationalde-mandsimposedbytheexactmethodsarerathersevere.WeandourcolleaguesattheHarvardSchoolofPublicHealthhaveworkedonthesecomputationalproblemsforoveradecadeandhavedevelopedexactandMonteCarloalgorithmstosolvethem.Thesealgorithmshav

7、enowbeenimplementedinExactTests.Forsmalldatasets,thealgorithmsensurequickcomputationofexactpvalues.Ifadatasetistoolargefortheexactalgorithms,MonteCarloalgorithmsaresubstitutedintheirplaceinordertoes-timatetheexactpvaluestoanydesiredlevelofaccuracy.Thesenume

8、ricalalgorithmsarefullyintegratedintotheIBM®SPSS®Statisticssystem.SimpleselectionsintheNonparametricTestsandCrosstabsdialogboxesal-lowyoutoobtainexactandMonteCarloresultsquicklyandeasily.Acknowledgment