Table Of Content

i IBM SPSS Conjoint 19 Note: Beforeusingthisinformationandtheproductitsupports,readthegeneralinformation under Notices on p. 39. ThisdocumentcontainsproprietaryinformationofSPSSInc,anIBMCompany. Itisprovided underalicenseagreementandisprotectedbycopyrightlaw. Theinformationcontainedinthis publicationdoesnotincludeanyproductwarranties,andanystatementsprovidedinthismanual shouldnot beinterpreted as such. WhenyousendinformationtoIBMorSPSS,yougrantIBMandSPSSanonexclusiveright touseordistributetheinformationinanywayitbelievesappropriatewithoutincurringany obligation to you. ©CopyrightSPSSInc. 1989,2010. Preface IBM®SPSS®Statisticsisacomprehensivesystemforanalyzingdata. TheConjointoptional add-onmoduleprovidestheadditionalanalytictechniquesdescribedinthismanual. TheConjoint add-onmodulemustbeusedwiththeSPSSStatisticsCoresystemandiscompletelyintegrated into that system. About SPSS Inc., an IBM Company SPSS Inc., an IBM Company, is a leading global provider of predictive analytic software andsolutions. Thecompany’scompleteportfolio ofproducts—data collection, statistics, modelinganddeployment—capturespeople’sattitudesandopinions, predictsoutcomesof futurecustomerinteractions,andthenactsontheseinsightsbyembeddinganalyticsintobusiness processes. SPSSInc. solutionsaddressinterconnectedbusinessobjectivesacrossanentire organizationbyfocusingontheconvergenceofanalytics,ITarchitecture,andbusinessprocesses. Commercial,government,andacademiccustomersworldwiderelyonSPSSInc. technologyas acompetitiveadvantageinattracting,retaining,andgrowingcustomers,whilereducingfraud andmitigatingrisk. SPSSInc. wasacquiredbyIBMinOctober2009. Formoreinformation, visit http://www.spss.com. Technical support Technical support is available to maintenance customers. Customers may contact Technical Support for assistance in using SPSS Inc. products or for installation help for one of the supported hardware environments. To reach Technical Support, see the SPSS Inc. web site at http://support.spss.comor find your local office via the web site at http://support.spss.com/default.asp?refpage=contactus.asp. Bepreparedtoidentifyyourself,your organization,andyoursupportagreementwhenrequestingassistance. Customer Service Ifyouhaveanyquestionsconcerningyourshipmentoraccount,contactyourlocaloffice,listed ontheWebsiteathttp://www.spss.com/worldwide. Pleasehaveyourserialnumberreadyfor identification. Training Seminars SPSSInc. providesbothpublicandonsitetrainingseminars. Allseminarsfeaturehands-on workshops. Seminarswillbeofferedinmajorcitiesonaregularbasis. Formoreinformationon theseseminars,contactyourlocaloffice,listedontheWebsiteathttp://www.spss.com/worldwide. ©CopyrightSPSSInc. 1989,2010 iii Additional Publications TheSPSSStatistics: GuidetoDataAnalysis,SPSSStatistics: StatisticalProceduresCompanion, andSPSSStatistics: AdvancedStatisticalProceduresCompanion,writtenbyMarijaNorušisand publishedbyPrenticeHall,areavailableassuggestedsupplementalmaterial. Thesepublications coverstatisticalproceduresintheSPSSStatisticsBasemodule, AdvancedStatisticsmodule andRegressionmodule. Whetheryouarejustgettingstartingindataanalysisorarereadyfor advancedapplications,thesebookswillhelpyoumakebestuseofthecapabilitiesfoundwithin theIBM®SPSS®Statisticsoffering. Foradditionalinformationincludingpublicationcontents andsamplechapters,pleaseseetheauthor’swebsite: http://www.norusis.com iv Contents 1 Introduction to Conjoint Analysis 1 TheFull-ProfileApproach. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 2 AnOrthogonalArray . ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 2 TheExperimentalStimuli. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 2 CollectingandAnalyzingtheData ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 2 Part I: User’s Guide 2 Generating an Orthogonal Design 5 DefiningValuesforanOrthogonalDesign. ... ... ... ... ... ... ... ... ... ... ... ... ... ... 6 OrthogonalDesignOptions... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 7 ORTHOPLANCommandAdditionalFeatures.. ... ... ... ... ... ... ... ... ... ... ... ... ... 8 3 Displaying a Design 9 DisplayDesignTitles.. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 10 PLANCARDSCommandAdditionalFeatures.. ... ... ... ... ... ... ... ... ... ... ... ... ... 10 4 Running a Conjoint Analysis 11 Requirements ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 11 SpecifyingthePlanFileandtheDataFile. ... ... ... ... ... ... ... ... ... ... ... ... ... 12 SpecifyingHowDataWereRecorded ... ... ... ... ... ... ... ... ... ... ... ... ... ... 12 OptionalSubcommands .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 13 v Part II: Examples 5 Using Conjoint Analysis to Model Carpet-Cleaner Preference17 GeneratinganOrthogonalDesign. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 17 CreatingtheExperimentalStimuli:DisplayingtheDesign . ... ... ... ... ... ... ... ... ... ... 21 RunningtheAnalysis . ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 23 UtilityScores . ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 25 Coefficients .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 25 RelativeImportance.. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 26 Correlations .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 27 Reversals. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 27 RunningSimulations.. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 28 PreferenceProbabilitiesofSimulations .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... 28 Appendices A Sample Files 30 B Notices 39 Bibliography 41 Index 43 vi Chapter 1 Introduction to Conjoint Analysis Conjointanalysisisamarketresearchtoolfordevelopingeffectiveproductdesign. Usingconjoint analysis,theresearchercananswerquestionssuchas: Whatproductattributesareimportantor unimportanttotheconsumer? Whatlevelsofproductattributesarethemostorleastdesirablein theconsumer’smind? Whatisthemarketshareofpreferenceforleadingcompetitors’products versusourexistingorproposedproduct? Thevirtueofconjointanalysisisthatitaskstherespondenttomakechoicesinthesamefashion astheconsumerpresumablydoes—bytradingofffeatures,oneagainstanother. Forexample,supposethatyouwanttobookanairlineflight. Youhavethechoiceofsittingina crampedseatoraspaciousseat. Ifthisweretheonlyconsideration,yourchoicewouldbeclear. Youwouldprobablypreferaspaciousseat. Orsupposeyouhaveachoiceofticketprices: $225or $800. Onpricealone,takingnothingelseintoconsideration,thelowerpricewouldbepreferable. Finally,supposeyoucantakeeitheradirectflight,whichtakestwohours,oraflightwithone layover,whichtakesfivehours. Mostpeoplewouldchoosethedirectflight. Thedrawbacktotheaboveapproachisthatchoicealternativesarepresentedonsingleattributes alone,oneatatime. Conjointanalysispresentschoicealternativesbetweenproductsdefinedby setsofattributes. Thisisillustratedbythefollowingchoice: wouldyoupreferaflightthatis cramped,costs$225,andhasonelayover,oraflightthatisspacious,costs$800,andisdirect? If comfort,price,anddurationaretherelevantattributes,therearepotentiallyeightproducts: Product Comfort Price Duration 1 cramped $225 2hours 2 cramped $225 5hours 3 cramped $800 2hours 4 cramped $800 5hours 5 spacious $225 2hours 6 spacious $225 5hours 7 spacious $800 2hours 8 spacious $800 5hours Giventheabovealternatives,product4isprobablytheleastpreferred,whileproduct5isprobably themostpreferred. Thepreferencesofrespondentsfortheotherproductofferingsareimplicitly determinedbywhatisimportanttotherespondent. Usingconjointanalysis,youcandetermineboththerelativeimportanceofeachattributeas wellaswhichlevelsofeachattributearemostpreferred. Ifthemostpreferableproductisnot feasibleforsomereason,suchascost,youwouldknowthenextmostpreferredalternative. If youhaveotherinformationontherespondents,suchasbackgrounddemographics,youmightbe abletoidentifymarketsegmentsforwhichdistinctproductscanbepackaged. Forexample,the ©CopyrightSPSSInc. 1989,2010 1 2 Chapter 1 businesstravelerandthestudenttravelermighthavedifferentpreferencesthatcouldbemetby distinct product offerings. The Full-Profile Approach Conjointusesthefull-profile(alsoknownasfull-concept)approach,whererespondentsrank, order, orscore a set ofprofiles, orcards, accordingtopreference. Eachprofile describesa completeproductorserviceandconsistsofadifferentcombinationoffactorlevelsforallfactors (attributes) of interest. An Orthogonal Array Apotentialproblemwiththefull-profileapproachsoonbecomesobviousifmorethanafew factorsareinvolvedandeachfactorhasmorethanacoupleoflevels. Thetotalnumberofprofiles resultingfromallpossiblecombinationsofthelevelsbecomestoogreatforrespondentstorankor scoreinameaningfulway. Tosolvethisproblem,thefull-profileapproachuseswhatistermeda fractionalfactorialdesign,whichpresentsasuitablefractionofallpossiblecombinationsof thefactorlevels. Theresultingset,calledanorthogonalarray,isdesignedtocapturethemain effectsforeachfactorlevel. Interactionsbetweenlevelsofonefactorwithlevelsofanother factor are assumed to be negligible. TheGenerateOrthogonalDesignprocedureisusedtogenerateanorthogonalarrayandis typicallythestartingpointofaconjointanalysis. Italsoallowsyoutogeneratefactor-level combinations,knownasholdoutcases,whichareratedbythesubjectsbutarenotusedtobuild thepreferencemodel. Instead,theyareusedasacheckonthevalidityofthemodel. The Experimental Stimuli Eachsetoffactorlevelsinanorthogonaldesignrepresentsadifferentversionoftheproductunder studyandshouldbepresentedtothesubjectsintheformofanindividualproductprofile. This helpstherespondenttofocusononlytheoneproductcurrentlyunderevaluation. Thestimuli shouldbestandardizedbymakingsurethattheprofilesareallsimilarinphysicalappearance exceptforthedifferentcombinationsoffeatures. CreationoftheproductprofilesisfacilitatedwiththeDisplayDesignprocedure. Ittakesa designgeneratedbytheGenerateOrthogonalDesignprocedure, orenteredbytheuser, and producesasetofproductprofilesinaready-to-useformat. Collecting and Analyzing the Data Sincethereistypicallyagreatdealofbetween-subjectvariationinpreferences,muchofconjoint analysisfocusesonthesinglesubject. Togeneralizetheresults,arandomsampleofsubjectsfrom thetargetpopulationisselectedsothatgroupresultscanbeexamined. Thesizeofthesampleinconjointstudiesvariesgreatly. Inonereport(CattinandWittink, 1982),theauthorsstatethatthesamplesizeincommercialconjointstudiesusuallyrangesfrom 100to1,000,with300to550themosttypicalrange. Inanotherstudy(AkaahandKorgaonkar, 3 IntroductiontoConjointAnalysis 1988),itisfoundthatsmallersamplesizes(lessthan100)aretypical. Asalways,thesamplesize shouldbelargeenoughtoensurereliability. Oncethesampleischosen,theresearcheradministersthesetofprofiles,orcards,toeach respondent. TheConjointprocedureallowsforthreemethodsofdatarecording. Inthefirst method,subjectsareaskedtoassignapreferencescoretoeachprofile. Thistypeofmethodis typicalwhenaLikertscaleisusedorwhenthesubjectsareaskedtoassignanumberfrom1to 100toindicatepreference. Inthesecondmethod,subjectsareaskedtoassignaranktoeach profilerangingfrom1tothetotalnumberofprofiles. Inthethirdmethod,subjectsareaskedto sorttheprofilesintermsofpreference. Withthislastmethod,theresearcherrecordstheprofile numbersintheordergivenbyeachsubject. AnalysisofthedataisdonewiththeConjointprocedure(availableonlythroughcommand syntax)andresultsinautilityscore,calledapart-worth,foreachfactorlevel. Theseutility scores,analogoustoregressioncoefficients,provideaquantitativemeasureofthepreference foreachfactorlevel, withlargervaluescorrespondingtogreaterpreference. Part-worthsare expressedinacommonunit,allowingthemtobeaddedtogethertogivethetotalutility,oroverall preference,foranycombinationoffactorlevels. Thepart-worthsthenconstituteamodelfor predictingthepreferenceofanyproductprofile, includingprofiles,referredtoassimulation cases,thatwerenotactuallypresentedintheexperiment. Theinformationobtainedfromaconjointanalysiscanbeappliedtoawidevarietyofmarket researchquestions. Itcanbeusedtoinvestigateareassuchasproductdesign, marketshare, strategicadvertising,cost-benefitanalysis,andmarketsegmentation. Althoughthefocusofthismanualisonmarketresearchapplications,conjointanalysiscan beusefulinalmostanyscientificorbusinessfieldinwhichmeasuringpeople’sperceptions or judgments is important. Part I: User’s Guide