2 The Research Enterprise in Psycho.ppt

Chapter2 TheResearchEnterpriseinPsychology Fig2 1 Theoryconstruction Agoodtheorywillgenerateahostoftestablehypotheses Inatypicalstudy onlyoneorafewofthesehypothesescanbeevaluated Iftheevidencesupportsthehypotheses ourconfidenceinthetheorytheywerederivedfromgenerallygrows Ifthehypothesesarenotsupported confidenceinthetheorydecreasesandrevisionstothetheorymaybemadetoaccommodatethenewfindings Ifthehypothesesgeneratedbyatheoryconsistentlyfailtogarnerempiricalsupport thetheorymaybediscardedaltogether Thus theoryconstructionandtestingisagradualprocess Fig2 2 Flowchartofstepsinascientificinvestigation AsillustratedinastudybyColeetal 1996 ascientificinvestigationconsistsofasequenceofcarefullyplannedsteps beginningwiththeformulationofatestablehypothesisandendingwiththepublicationofthestudy ifitsresultsareworthyofexaminationbyotherresearchers TheScientificMethod Terminology OperationaldefinitionsareusedtoclarifypreciselywhatismeantbyeachvariableParticipantsorsubjectsaretheorganismswhosebehaviorissystematicallyobservedinastudyDatacollectiontechniquesallowforempiricalobservationandmeasurementStatisticsareusedtoanalyzedataanddecidewhetherhypothesesweresupportedFindingsaresharedthroughreportsatscientificmeetingsandinscientificjournals periodicalsthatpublishtechnicalandscholarlymaterialAdvantagesofthescientificmethod clarityofcommunicationandrelativeintoleranceoferrorResearchmethods generalstrategiesforconductingscientificstudies ExperimentalResearch LookingforCauses Experiment manipulationofonevariableundercontrolledconditionssothatresultingchangesinanothervariablecanbeobservedDetectionofcause and effectrelationshipsIndependentvariable IV variablemanipulatedDependentvariable DV variableaffectedbymanipulationHowdoesXaffectY X IndependentVariable andY DependentVariable ExperimentalandControlGroups TheLogicoftheScientificMethod Experimentalgroup subjectswhoreceivesomespecialtreatmentinregardtotheindependentvariableControlgroup similarsubjectswhodonotreceivethespecialtreatmentLogic Twogroupsalikeinallrespects randomassignment ManipulateindependentvariableforonegrouponlyResultingdifferencesinthetwogroupsmustbeduetotheindependentvariableExtraneousandconfoundingvariables Fig2 5 Thebasicelementsofanexperiment AsillustratedbytheSchachterstudy thelogicofexperimentaldesignrestsontreatingtheexperimentalandcontrolgroupsexactlyalike tocontrolforextraneousvariables exceptforthemanipulationoftheindependentvariable Inthisway theexperimenterattemptstoisolatetheeffectsoftheindependentvariableonthedependentvariable ExperimentalDesigns Variations ExposeasinglegrouptotwodifferentconditionsReducesextraneousvariablesManipulatemorethanoneindependentvariableAllowsforstudyofinteractionsbetweenvariablesUsemorethanonedependentvariableObtainsamorecompletepictureofeffectoftheindependentvariable Fig2 6 Manipulationoftwoindependentvariablesinanexperiment Asthisexampleshows whentwoindependentvariablesaremanipulatedinasingleexperiment theresearcherhastocomparefourgroupsofsubjects orconditions insteadoftheusualtwo Themainadvantageofthisprocedureisthatitallowsanexperimentertoseewhethertwovariablesinteract StrengthsandWeaknessesofExperimentalResearch Strengths conclusionsaboutcause and effectcanbedrawnWeaknesses artificialnatureofexperimentsethicalandpracticalissues Descriptive CorrelationalMethods LookingforLinks MethodsusedwhenaresearchercannotmanipulatethevariablesunderstudyNaturalisticobservationCasestudiesSurveysAllowresearcherstodescribepatternsofbehavioranddiscoverlinksorassociationsbetweenvariablesbutcannotimplycausation Fig2 11 Comparisonofmajorresearchmethods Thischartpullstogetheragreatdealofinformationonkeyresearchmethodsinpsychologyandgivesasimpleexampleofhoweachmethodmightbeappliedinresearchonaggression Asyoucansee thevariousresearchmethodseachhavestrengthsandweaknesses StatisticsandResearch DrawingConclusions Statistics usingmathematicstoorganize summarize andinterpretnumericaldataDescriptivestatistics organizingandsummarizingdataInferentialstatistics interpretingdataanddrawingconclusions DescriptiveStatistics MeasuresofCentralTendency Measuresofcentraltendency typicaloraveragescoreinadistributionMean arithmeticaverageofscoresMedian scorefallingintheexactcenterMode mostfrequentlyoccurringscoreWhichmostaccuratelydepictsthetypical Fig2 12 Measuresofcentraltendency Thethreemeasuresofcentraltendencyusuallyconverge butthatisnotalwaysthecase asthesedataillustrate Whichmeasureismostusefuldependsonthenatureofthedata Generally themeanisthebestindexofcentraltendency butinthisinstancethemedianismoreinformative DescriptiveStatistics Variability Variability howmuchscoresvaryfromeachotherandfromthemeanStandarddeviation numericaldepictionofvariabilityHighvariabilityindataset highstandarddeviationLowvariabilityindataset lowstandarddeviation Fig2 13 Variabilityandthestandarddeviation Althoughthesetwosetsofdataproducethesamemean oraverage anobserveronWildStreetwouldseemuchmorevariabilityinthespeedsofindividualcarsthananobserveronPerfectionBoulevardwould Asyoucansee thestandarddeviationforsetBishigherthanthatforsetAbecauseofthegreatervariabilityinsetB DescriptiveStatistics Correlation Whentwovariablesarerelatedtoeachother theyarecorrelated Correlation numericalindexofdegreeofrelationshipCorrelationexpressedasanumberbetween0and1CanbepositiveornegativeNumberscloserto1 or indicatestrongerrelationship Fig2 15 Interpretingcorrelationcoefficients Themagnitudeofacorrelationcoefficientindicatesthestrengthoftherelationshipbetweentwovariables Thesign plusorminus indicateswhetherthecorrelationispositiveornegative Thecloserthecoefficientcomesto 1 00or 1 00 thestrongertherelationshipbetweenthevariables Correlation Prediction NotCausation Highercorrelationcoefficients increasedabilitytopredictonevariablebasedontheotherSAT ACTscoresmoderatelycorrelatedwithfirstyearcollegeGPA2variablesmaybehighlycorrelated butnotcausallyrelatedFootsizeandvocabularypositivelycorrelatedDolargerfeetcauselargervocabularies Thethirdvariableproblem Fig2 16 Threepossiblecausalrelationsbetweencorrelatedvariables IfvariablesXandYarecorrelated doesXcauseY doesYcauseX ordoessomehiddenthirdvariable Z accountforthechangesinbothXandY Astherelationshipbetweensmokinganddepressionillustrates acorrelationalonedoesnotprovidetheanswer Wewillencounterthisproblemofinterpretingthemeaningofcorrelationsfrequentlyinthistext InferentialStatistics InterpretingDataandDrawingConclusions Hypothesistesting doobservedfindingssupportthehypotheses Arefindingsrealorduetochance Statisticalsignificance whentheprobabilitythattheobservedfindingsareduetochanceisverylowVerylow lessthan5chancesin100 05level EvaluatingResearch MethodologicalPitfalls SamplingbiasPlaceboeffectsDistortionsinself reportdata SocialdesirabilitybiasResponsesetExperimenterbiasthedouble blindsolution Fig2 17 Therelationshipbetweenthepopulationandthesample Theprocessofdrawinginferencesaboutapopulationbasedonasampleworksonl