SPSSExercise6CentralTendency

Due:Centraltendencyreferstomeasuresusedtoassesstheaverageofobservations.Thesemeasuresincludemode,median,andmean.Modedescribestheattributeofavariablethatappearsmostfrequently.Mediandescribes,inanordinal,interval,orratiovariable,themiddlevalue.Meandescribesthemathematicalaverage.Objective:

1. LearntocalculatethemeasuresofcentraltendencyusingSPSS2. Learnhowtochoosethecorrectmeasureofcentraltendency.(In

conjunctionwithclasslecture)3. Learntointerpretcentraltendencyoutput.(Inconjunctionwithclass

lecture)4. Learntopresentmeasuresofcentraltendencyinatable

SPSSProcedure:

1. OpenthedatasetinSPSS2. FromthetoolbarselectAnalyze>DescriptiveStatistics>Frequencies.See

Figure6.1.Thiswillcauseawindowtoopenup.SeeFigure6.2.3. Inthe“Frequencies”windowselect“Statistics.”Thiswillcauseawidow

similartothatinFigure6.3tocomeup.4. Inthe“Frequencies:Statistics”windowselect“Mean,”“Median,”and“Mode”

asshowninFigure6.3.Select“Continue.”5. Inthe“Frequencies”windowunchecktheboxinthebottomlefthandcorner

thatsays“Displayfrequencytables.”6. Select“OK”andtheoutputwillappear(seeFigure6.4).

ReadingtheOutput:Thecolumnsintheoutputwindowdisplaythesamedata(seeFigure6.4).Atthetopisthevariablenamefollowedbythevalidfrequency,themissingfrequency,themean,median,andmode.Notethatshouldanymeasureofcentraltendencyhaveavaluethatishigherorlowerthanavalueassociatedwithavariablethenthereislikelysomekindoferror.Thinkofitthisway:ifastudenthastakenthreeexamswiththescoresof75,80,and85thenitisnotpossibleforthestudenttohaveanexamaveragethatislowerthana75orhigherthanan85.DisplayingData:SeeTable6.1forasampleofwhatacentraltendencytablemightlooklike.NotethatunlikeinSPSSoutput,thevariablesarepresentedincolumnsasopposedtorows.Thisisdonesothatseveralmeasurescanbepresentedatthesametimeinonetable.StudentsareREQUIREDtofollowthispractice.

AnalyzingCentralTendency:Measuresofcentraltendencyarebestselectedbyconsideringthelevelofmeasurementofavariable.Usingthefollowingtabletodecidewhichmeasureisbest.

Nominal Ordinal Interval/Ratio

Mode Best OK OK

Median No Best OK

Mean No No Best

Assignment:

1. Producemeasuresofcentraltendencyforthevariables::“age,”“partyid,”“hlth5,”“empathy5r,”“ager,”and“empathyindex.”

2. Makeatabletopresentthedatafromthevariablesinstep1.3. Writeareportwiththefollowing:

a. Describethemeasuresofcentraltendencyandhowtheyarecalculated.

b. Describehowthebestmeasureofcentraltendencyisselectedforavariable.

c. Analysisofthetableyoucreated.Thisincludesselectingthemeasurethatismostappropriategiventhevariable,explainingwhyitisthemostappropriate,andanalysisofwhatthemeasuremeans

4. Acopyoftableandtheoutput.

Figure6.1.

Figure6.2.

Figure6.3.

Figure6.4.

Table6.1.CentralTendencyMeasures Mean Median ModeMarital 2.35 1 1Age 45.96 44 40Empathy1 4.12 4 5n=2,812Source:2004GeneralSocialSurvey