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April 15 Tuesday Q1 revisited noon to 3:30 armory 270E5 April 24th E6 May 13May 6th assignment 1 hard copy and compass – course content – A2Descriptive vs experimental researchDescriptive – at a particular point in timeExperimental – moves beyond description to determine causality (goal)Causality is the effect of changes in one area on one or more other areas. Research to explore consumer reactions to banner ads: What aspects of banner ads are most likely to influence a click through?Additional experimental insightsRelationships between discount codes and relevanceDiscount codes only important when level of relevance is lowRelationship between ad size and relevanceAd size is only important when ads do not contain a discount codeLimitations of survey researchSurvey results become less reliable for explaining behaviors whenQuestions require recall, especially over long periodsIndividuals are asked for introspection in areas of behavior not normally thought aboutIndividuals are asked to use memory to attribute cause and effectThere may be complex, multiple, or interrelated influences on behaviorClassical experimentMajor components:Independent and dependent variablesPre testing and post testingExperimental and control groupsIndependent and dependent variablesEffects of x on y Where x and y are variables (liable to variable or change)Y is dependent, x is independentDV refers to status of the effectIV refers to the presumed cause – takes the form of a stimulusPre test and post testPretesting –the measurement of a DV among participantsPost testing – the measurement of a DV among participants after they have been exposedExperiemental and control groupsExperimental group – group of subjects to whom an experimental stimulus is administeredControl group – group of subjects to whom no experimental stimulus is administered an who should resemble the experimental group in all other respectsSteps in experimentation Identify what you need to learnTake relevant actions (intervention or manipulation)Observe effects and consequencesDetermine causalityComponents of an experimentAt least one independent variableAt least one dependent variableAt least one manipulationWhat defines a true experimentControlled arrangement and manipulation of the conditions (treatments)Random assignment of treatments to the sampling units Anything else is quasi-experimentWhy randomize?Protect against unsuspected sources of biasNo guarantee, but an attempt to equalize groupsRequirements for causalityEvents must take place in proper orderEvents must show an explicit relationshipAlternative explanations must be reduced or eliminatedMust eliminate other explanationsRelationship must show strength of associationThree imperatives for establishing causual relationshipsCovariationChanges in iv must correspond with changes in dvTemporal precedenceFor iv to have caused dv, iv must have occurred before dvInternal validityValidityInternal validity refers to our ability to attribute the observed effect to the independent variables and not other variablesExternal validity refers to extent to which the results of an experiment can be generalized, or extended, to other situations, populations, timesThreats to internal validityHistory maturationTestingInstrumentationSelectionMortalityHistoryAny events or influences beyond those intentionally manipulated by researcher which havepotential to affect experimental outcomeMaturationPeople are always changing, which may affect the dynamics of the experiment (get older, stronger, wiser, etc)TestingMeasurement is likely to influence people’s behaviorTesting effect – pretest affects posttest (practice improves performance)Interactive testing effect: pretest affects perceptions of treatment (pretest changes the waypeople respond to the stimulus)InstrumentationSpecifics of the measures researchers employ will affect the resultsSelectionThe types of subjects selected for the study will affect the resultsMortalitySubjects drop out during the cource of experiementResearcher bias errorOccurs when actions of experiementer bias outcome of the experiementCan be intentional or unintentional.Double blind experimentNeither the subjects nor the experimenters know which is the experimental and which is the control groupQuasi experimental designsOne shot case study – a single group of subjects is measured on a dependent variable following an experiemental stimulusOne group pretest post test design – a pretest is added for the experimental group but lacksa control groupStatic group comparison – includes experiemental and control groups, but no pretestTrue experimental designsControl group & Stimulated pre test to post testWeek 12:- E5 4/24 – Thursdayo Many math items- A2) submission – may 6th start of classo Hardcopy stapledo Safeassign – compass c ourse content  a2 - E6 cummulative exam 6 is may 13 – Tuesday 2-3:50pm - Q2 coming soon – 70 pts o Math questions/scantron - Bring calculator!Agenda:- Experimentation, experimentso Factorial designso Internal/external validity- Descriptive statistics o Mean, standard deviation, correlation, modeFactorial designs:- Allows for manipulation of two or more independent variables at the same timeo Each variable has two or more levels or aspects Ex. Type of spokesperson- Celebrity – celebrity in serious commercial, celebrity in humorous commercial- Regular – regular person in serious commercial, regular person in humorous commercial Ex. Effects of advertising copy on sensory thoughts and perceived taste:- Study 2 – potato chips (IN PREVIOUS NOTES, WEEK 11)- Study two – different food item, different operationalization- Single: our potato chips deliver taste you crave. o Single sensory thought/stimulus o Single condition focuses on taste only - Multiple: smell & crunchy textureo Multiple sensory thoughts - Results: 1 – very poor taste, 9 = very good tasteo Multiple = almost 7o Single = around 5.5 o Additional example: Study 2 – the experiment used a one-factor between-subjects subjects design with the ad (multiple sense or single sense) serving as the manipulated factor- One factor = one IV- Between-subjects = participants administered only one treatment (e.g. within subjects = participants administered both treatments, usually one after the other) Sensory thoughts  taste perceptions- Study 3: A2 (ad: multiple sense or single sense) x2 (cognitive load: yes or no) between-subjects full factorial design

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UIUC ADV 281 - Descriptive vs experimental research

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