Medical Statistics: A Guide to SPSS, Data Analysis and Critical Appraisal

411 Pages·2014·2.57 MB·English

by  Jennifer Peat

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Medical Statistics
A Guide to SPSS, Data Analysis and Critical Appraisal
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Medical
Statistics
A Guide to SPSS, Data Analysis
and Critical Appraisal
Second Edition
Belinda Barton
Children’sHospitalEducationResearchInstitute,TheChildren’sHospitalatWestmead,
Sydney,Australia
Jennifer Peat
HonoraryProfessor,AustralianCatholicUniversityandResearchConsultant,
Sydney,Australia
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Thiseditionfirstpublished2014©2014byJohnWiley&SonsLtd.
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Contents
Introduction,ix
Acknowledgements,xiii
Aboutthecompanionwebsite,xv
Chapter1 CreatinganSPSSdatafileandpreparingtoanalysethedata,1
1.1 CreatinganSPSSdatafile,1
1.2 OpeningdatafromExcelinSPSS,6
1.3 Categoricalandcontinuousvariables,7
1.4 Classifyingvariablesforanalyses,7
1.5 HypothesistestingandPvalues,8
1.6 Choosingthecorrectstatisticaltest,9
1.7 Samplesizerequirements,10
1.8 Studyhandbookanddataanalysisplan,12
1.9 Documentation,13
1.10 Checkingthedata,13
1.11 Avoidingandreplacingmissingvalues,14
1.12 SPSSdatamanagementcapabilities,16
1.13 ManagingSPSSoutput,20
1.14 SPSShelpcommands,21
1.15 Goldenrulesforreportingnumbers,21
1.16 Notesforcriticalappraisal,21
References,23
Chapter2 Descriptivestatistics,24
2.1 Parametricandnon-parametricstatistics,25
2.2 Normaldistribution,25
2.3 Skeweddistributions,26
2.4 Checkingfornormality,29
2.5 Transformingskewedvariables,43
2.6 Dataanalysispathway,49
2.7 Reportingdescriptivestatistics,49
2.8 Checkingfornormalityinpublishedresults,50
2.9 Notesforcriticalappraisal,51
References,51
Chapter3 Comparingtwoindependentsamples,52
3.1 Comparingthemeansoftwoindependentsamples,52
3.2 One-andtwo-sidedtestsofsignificance,54
3.3 Effectsizes,55
3.4 Studydesign,57
3.5 Influenceofsamplesize,58
3.6 Two-samplet-test,71
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vi Contents
3.7 Confidenceintervals,73
3.8 Reportingtheresultsfromtwo-samplet-tests,75
3.9 Rank-basednon-parametrictests,80
3.10 Notesforcriticalappraisal,88
References,89
Chapter4 Pairedandone-samplet-tests,90
4.1 Pairedt-tests,90
4.2 Non-parametrictestforpaireddata,97
4.3 Standardizingfordifferencesinbaselinemeasurements,99
4.4 Single-samplet-test,102
4.5 Testingforabetween-groupdifference,106
4.6 Notesforcriticalappraisal,110
References,111
Chapter5 Analysisofvariance,112
5.1 BuildingANOVAandANCOVAmodels,113
5.2 ANOVAmodels,113
5.3 One-wayanalysisofvariance,117
5.4 EffectsizeforANOVA,127
5.5 Post-hoctestsforANOVA,128
5.6 Testingforatrend,133
5.7 Reportingtheresultsofaone-wayANOVA,134
5.8 FactorialANOVAmodels,135
5.9 Anexampleofathree-wayANOVA,140
5.10 Analysisofcovariance(ANCOVA),145
5.11 TestingthemodelassumptionsofANOVA/ANCOVA,149
5.12 ReportingtheresultsofanANCOVA,158
5.13 Notesforcriticalappraisal,158
References,160
Chapter6 Analysesoflongitudinaldata,161
6.1 Studydesign,161
6.2 Samplesizeandpower,162
6.3 Covariates,163
6.4 AssumptionsofrepeatedmeasuresANOVAandmixed
models,163
6.5 Repeatedmeasuresanalysisofvariance,164
6.6 Linearmixedmodels,182
6.7 Notesforcriticalappraisal,195
References,196
Chapter7 Correlationandregression,197
7.1 Correlationcoefficients,197
7.2 Regressionmodels,205
7.3 Multiplelinearregression,213
7.4 Interactions,230
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Contents vii
7.5 Residuals,235
7.6 Outliersandremotepoints,237
7.7 Validatingthemodel,240
7.8 Reportingamultiplelinearregression,241
7.9 Non-linearregression,242
7.10 Centering,244
7.11 Notesforcriticalappraisal,247
References,247
Chapter8 Ratesandproportions,249
8.1 Summarizingcategoricalvariables,249
8.2 Describingbaselinecharacteristics,251
8.3 Incidenceandprevalence,252
8.4 Chi-squaretests,253
8.5 2×3Chi-squaretables,260
8.6 Cellswithsmallnumbers,262
8.7 Exactchisquaretest,263
8.8 Numberofcellsthatcanbetested,264
8.9 Reportingchi-squaretestsandproportions,266
8.10 Largecontingencytables,267
8.11 Categorizingcontinuousvariables,271
8.12 Chi-squaretrendtestfororderedvariables,273
8.13 Numberneededtotreat(NNT),277
8.14 Pairedcategoricalvariables:McNemar’schi-squaretest,281
8.15 Notesforcriticalappraisal,285
References,286
Chapter9 Riskstatistics,287
9.1 Riskstatistics,287
9.2 Studydesign,288
9.3 Oddsratio,288
9.4 Protectiveoddsratios,296
9.5 Adjustedoddsratios,298
9.6 Relativerisk,308
9.7 Numberneededtobeexposedforoneadditionalpersonto
beharmed(NNEH),312
9.8 Notesforcriticalappraisal,312
References,313
Chapter10 Testsofreliabilityandagreement,314
10.1 Reliabilityandagreement,314
10.2 Kappastatistic,317
10.3 Reliabilityofcontinuousmeasurements,321
10.4 Intra-classcorrelation,322
10.5 Measuresofagreement,325
10.6 Notesforcriticalappraisal,329
References,329
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Chapter11 Diagnosticstatistics,331
11.1 Codingfordiagnosticstatistics,331
11.2 Positiveandnegativepredictivevalues,332
11.3 Sensitivityandspecificity,335
11.4 Likelihoodratio,338
11.5 ReceiverOperatingCharacteristic(ROC)Curves,339
11.6 Notesforcriticalappraisal,348
References,349
Chapter12 Survivalanalyses,350
12.1 Studydesign,351
12.2 Censoredobservations,351
12.3 Kaplan–Meiersurvivalmethod,351
12.4 Coxregression,360
12.5 Questionsforcriticalappraisal,368
References,368
Glossary,370
Usefulwebsites,381
Index,385