experimental and non- experimental research in
TRANSCRIPT
• RajinderKoul,Ph.D.,CCC‐SLP• ProfessorandChairperson• DepartmentofSpeech,LanguageandHearingSciences• TexasTechUniversityHealthSciencesCenter
EXPERIMENTAL AND NON-EXPERIMENTAL RESEARCH IN BEHAVIORAL SCIENCES: IMPLICATIONS FOR PRACTICE
UNIVERSITY OF PRETORIACENTRE FOR AUGMENTATIVE AND ALTERNATIVE COMMUNICATION (CAAC)
RESEARCH DESIGNResearchdesignsareastructureoftemporal‐spatialarrangementswithinwhichtheselectedvariablesarecontrolled,manipulated,andmeasured(Hegde,2003).
Researchdesignshelprevealrelationshipsbetweenandamongvariables: Independent:notrelated Cause‐effectrelationships Correlativerelationships Interactiverelationships:multiplevariablescombinetogethertoproduceaneffect;thetotaloutcomeistypicallygreaterthanthemereadditiveeffects
NON‐EXPERIMENTAL RESEARCH
Lackofcontroloverextraneousand/orassignedindependentvariables(IVs)
Independentvariablesarenotintroduced,withdrawn,ormanipulated
Relationshipbetweencauseandeffectcannotbeestablished
EX‐POST FACTO RESEARCH
EX‐POST FACTO
Ex‐PostFactoResearch(afterthefact,“retrospectivesearch”) Independentvariableshaveoccurredinthepast‐ oneisstudyingthedependentvariable(DVs)
Unabletodeducecause‐effectrelationshipsbecauseindependentvariablescannotbemanipulated
Casehistorymethod
EX‐POST FACTO
Weaknesses ItisnotexperimentalbecauseIVsarenotmanipulated
LackscontrolbecauseextraneousIVsarenotruledout(internalvalidityconcerns)
CannotsupporttheoryStatisticalcorrelations
EX‐POST FACTO
AdvantagesUncoversimportantvariablesExploratoryscienceSocialvs.scientificviewpoint
NORMATIVE RESEARCH
NORMATIVE RESEARCH
AlsocalleddevelopmentalordescriptiveresearchDistributionofselecteddependentvariablesacrossdifferentagegroupsisobservedandrecorded
Helpsdifferentiatetypicalfromatypical(standardizedtests)
HelpsguideclinicalinterventionNotabletomanipulateIndependentvariablesandthuscannotdrawcause‐effectrelationship
NORMATIVE RESEARCH
Howtoconduct: IdentifypopulationDrawarepresentativesample(i.e.,allparticipantshaveanequalchanceofparticipatinginthisstudy)
SamplethebehaviorofselectedparticipantsGeneralizeresultstothepopulation
NORMATIVE RESEARCH
WeaknessesDifficultyobtainingtruerandomsamples Inadequate(brief)samplingofresponsesDoesnotsupportatheory
TwoTypesCrossSectionalresearchLongitudinalresearch
STANDARD‐GROUP COMPARISONS
STANDARD‐GROUP COMPARISON
Extensionofnormativeresearch GroupsareformedonthebasisofoneDVand
arethencomparedonthebasisofthesameoranotherDV
TwostrategiestoperformStandard‐GroupComparison:
1. Criterionandcomparisonmeasuresarethesame2. Criterionandcomparisonmeasuresaredifferent
STANDARD‐GROUP COMPARISON
Strengths:CandescribedifferencesHelpsdistinguishclinicalgroups
Weaknesses:Cannotassigncause/effectrelationshipsCannotmanipulateIV
CohortStudiesandCase‐controlstudiesarevariationsofStandard‐groupcomparisonresearch
SURVEY RESEARCH
Assesssomefeaturesofagroupofpeopleoraparticularsociety
DistributionofDVinthepopulationisdetermined(+or‐)4‐6%rangeoferror
Errorratedependsupontherepresentativenatureofthesample
Realthoughtsandactionsmaynotbethesameasopinionsandattitudes
EXPERIMENTAL RESEARCH
EXPERIMENTAL RESEARCH
ControlledarrangementinwhichoneormoreIVsaremanipulatedandtheeffectsofsuchmanipulationontheDVsaremeasuredCanisolatecause/effectrelationship(seekstoexplainaneventbydiscoveringitscausalvariables)
Control‐canruleoutcompetinghypothesisCanexplainphenomenaandsupporttheories
EXPERIMENTAL RESEARCH
Twovarieties:BasicandAppliedResearchClinical:usedtodescriberesearchthatisinsomewayconnectedwithdiseasesanddisorders;researchaimedatunderstandingandtreatingvariousdisordersofcommunicationisclinical
Applied:non‐clinicalasinbuildingbetterbridgesorsaferhighways
EXPERIMENTAL RESEARCH
BasicResearch:Givesusinsightstodoappliedresearch‐veryimportantOftentheoretical
EXPERIMENTAL RESEARCH
Twostrategiestoruleoutextraneousvariablesa) Groupstrategyb) Singlesubjectstrategy
EXPERIMENTAL RESEARCH‐BETWEEN GROUP STRATEGYIngroupdesigns,youcomparemeansandstandarddeviationsof2ormoregroupsondependentvariablesofinterest(e.g.,randomizedcontroltrials)
Useinferentialstatisticstoseeifthedifferencesacrossthegroupsaresignificant.
Taketheaverageperformanceandcompareacrossgroups,thendetermineifthegroupsaredifferent.
EXPERIMENTAL RESEARCH‐BETWEEN GROUP STRATEGY
Randomization:randomselectionandassignment
Matching:MatchingpairsofparticipantsEquivalentfrequencydistribution‐matchedonastatisticalbasisGroupsareequalonassignedvariablesexceptontheIVthatoneismanipulated
EXPERIMENTAL RESEARCH‐BETWEEN GROUP STRATEGY
Wellcontrolledgroupdesignshaveatleasttwogroups(onecontrolandoneexperimental)
Majorityofgroupdesignsmeasurepre/posttestdifferences
Groupdesignshaveinferentialgenerality(sampletothepopulation),notlogicalgenerality
EXPERIMENTAL RESEARCH‐BETWEEN GROUP STRATEGY
Typesofgroupdesigns:Pre‐ExperimentalDesignsTrueExperimentalDesignsQuasi‐experimentaldesignsCorrelationalDesigns
TREATMENT RESEARCH
Uncontrolledtreatmentresearch (e.g.,casestudies)Controlledtreatmentresearch‐establishacause/effectrelationshipbetweentreatmenttechniqueandtheDV(i.e.,positivechangesinthepatientswhoreceiveit)
Directlyreplicatedtreatmentresearch‐sameinvestigators,originalsetting,differentsubjects(samemethodology)
Systematicallyreplicatedtreatmentresearch‐othercliniciansinothersettings
EVIDENCE HIERARCHY
QUESTIONS/DISCUSSION
