Chapter 12 Experimental Research © 2010 South-Western/Cengage Learning. All rights reserved. May...

Chapter 12Chapter 12Experimental Experimental

ResearchResearch

EIGHTH EDITION

BUSINESS MARKET RESEARCH

ZIKMUND BABINCARR GRIFFIN

LEARNING OUTCOMESLEARNING OUTCOMESLEARNING OUTCOMESLEARNING OUTCOMES

1.1. Identify the independent variable, dependent Identify the independent variable, dependent variable, and construct a valid simple variable, and construct a valid simple experiment to assess a cause and effect experiment to assess a cause and effect relationshiprelationship

2.2. Understand and minimize experimental errorUnderstand and minimize experimental error

3.3. Know ways of minimizing experimental Know ways of minimizing experimental demand characteristicsdemand characteristics

4.4. Avoid unethical experimental practicesAvoid unethical experimental practices

After studying this chapter, you should be able to

LEARNING OUTCOMES (cont’d)LEARNING OUTCOMES (cont’d)LEARNING OUTCOMES (cont’d)LEARNING OUTCOMES (cont’d)

5.5. Understand the advantages of a between-Understand the advantages of a between-subjects experimental design subjects experimental design

6.6. Weigh the trade-off between internal and Weigh the trade-off between internal and external validityexternal validity

7.7. Use manipulations to implement a completely Use manipulations to implement a completely randomized experimental design, a randomized experimental design, a randomized-block design, and a factorial randomized-block design, and a factorial experimental designexperimental design

After studying this chapter, you should be able to

Creating an ExperimentCreating an Experiment

• SubjectsSubjects The sampling units for an experiment, usually human The sampling units for an experiment, usually human

respondents who provide measures based on the respondents who provide measures based on the experimental manipulation.experimental manipulation.

• Independent VariablesIndependent Variables Experimental conditionsExperimental conditions

One of the possible levels of an experimental (independent) One of the possible levels of an experimental (independent) variable manipulation.variable manipulation.

Blocking variablesBlocking variables Variables included in the statistical analysis as a way of Variables included in the statistical analysis as a way of

controlling or accounting for variance due to that variable:controlling or accounting for variance due to that variable: Categorical variablesCategorical variables

EXHIBIT 12.EXHIBIT 12.11 Experimental Conditions in Self-Efficacy ExperimentExperimental Conditions in Self-Efficacy Experiment

Creating an Experiment (cont’d)Creating an Experiment (cont’d)

• Main EffectMain Effect The experimental difference in dependent variable The experimental difference in dependent variable

means between the different levels of any single means between the different levels of any single experimental variable.experimental variable.

• Interaction EffectInteraction Effect Differences in dependant variable means due to a Differences in dependant variable means due to a

specific combination of independent variables.specific combination of independent variables.

EXHIBIT 12.EXHIBIT 12.22 Job Satisfaction Means in Self-Efficacy ExperimentJob Satisfaction Means in Self-Efficacy Experiment

EXHIBIT 12.EXHIBIT 12.33 Experimental Graph Showing Results within Each ConditionExperimental Graph Showing Results within Each Condition

Designing an Experiment to Minimize Designing an Experiment to Minimize Experimental ErrorExperimental Error• Manipulation of the Independent VariableManipulation of the Independent Variable

Experimental treatment: the way an experimental Experimental treatment: the way an experimental variable is manipulated.variable is manipulated. Categorical variables: described by class or qualityCategorical variables: described by class or quality Continuous variables: described by quantity (level)Continuous variables: described by quantity (level)

Experimental GroupExperimental Group A group of subjects to whom an experimental treatment is A group of subjects to whom an experimental treatment is

administered.administered.

Control GroupControl Group A group of subjects to whom no experimental treatment is A group of subjects to whom no experimental treatment is

administered.administered.

Designing an Experiment (cont’d)Designing an Experiment (cont’d)

• More than One Independent VariableMore than One Independent Variable Cell:Cell: a specific treatment combination associated with a specific treatment combination associated with

an experimental group.an experimental group.

Computation of the number of cells in an Computation of the number of cells in an experiment:experiment:

KK = ( = (TT11)()(TT22)..()..(TTmm))

• Repeated MeasuresRepeated Measures Experiments in which an individual subject is exposed Experiments in which an individual subject is exposed

to more than one level of an experimental treatment.to more than one level of an experimental treatment.

• Selection and Measurement of the Dependent Selection and Measurement of the Dependent VariableVariable Selecting dependent variables that are relevant and Selecting dependent variables that are relevant and

truly represent an outcome of interest is crucial.truly represent an outcome of interest is crucial.

Choosing the right dependent variable is part of the Choosing the right dependent variable is part of the problem definition process.problem definition process. Thorough problem definition will help the researcher select Thorough problem definition will help the researcher select

the most important dependent variable(s).the most important dependent variable(s).

• Selection and Assignment of Test UnitsSelection and Assignment of Test Units Test unitsTest units: the subjects or entities whose responses : the subjects or entities whose responses

to treatment are measured or observed.to treatment are measured or observed.

• Sample Selection And Random Sampling ErrorsSample Selection And Random Sampling Errors Systematic or nonsampling errorSystematic or nonsampling error

Subject selection, experimental design, and unrecognized Subject selection, experimental design, and unrecognized extraneous variablesextraneous variables

Overcoming sampling errorsOvercoming sampling errors RandomizationRandomization MatchingMatching Control over extraneous variablesControl over extraneous variables

• Sample Selection And Random Sampling ErrorsSample Selection And Random Sampling Errors Experimental ConfoundExperimental Confound

When there is an alternative explanation beyond the When there is an alternative explanation beyond the experimental variables for any observed differences in the experimental variables for any observed differences in the dependent variable.dependent variable.

Once a potential confound is identified, the validity of the Once a potential confound is identified, the validity of the experiment is severely questioned.experiment is severely questioned.

Extraneous variablesExtraneous variables Variables that naturally exist in the environment that may Variables that naturally exist in the environment that may

have some systematic effect on the dependent variable.have some systematic effect on the dependent variable.

Demand CharacteristicsDemand Characteristics

• Demand CharacteristicDemand Characteristic An experimental design element or procedure that An experimental design element or procedure that

unintentionally provides subjects with hints about the unintentionally provides subjects with hints about the research hypothesis.research hypothesis.

• Demand EffectDemand Effect Occurs when demand characteristics actually affect Occurs when demand characteristics actually affect

the dependent variable.the dependent variable.

• Hawthorne EffectHawthorne Effect People will perform differently from normal when they People will perform differently from normal when they

know they are experimental subjects.know they are experimental subjects.

Reducing Demand EffectsReducing Demand Effects

Establishing ControlEstablishing Control

• Constancy of ConditionsConstancy of Conditions Subjects in all experimental groups are exposed to Subjects in all experimental groups are exposed to

identical conditions except for the differing identical conditions except for the differing experimental treatments.experimental treatments.

• CounterbalancingCounterbalancing Attempts to eliminate the confounding effects of order Attempts to eliminate the confounding effects of order

of presentation by varying the order of presentation of presentation by varying the order of presentation (exposure) of treatments to subject groups.(exposure) of treatments to subject groups.

Ethical Issues in ExperimentationEthical Issues in Experimentation

• Debriefing experimental subjectsDebriefing experimental subjects Communicating the purpose of the experimentCommunicating the purpose of the experiment Explaining the researcher’s hypotheses Explaining the researcher’s hypotheses

• Attempts to interfere with a competitor’s test-Attempts to interfere with a competitor’s test-marketing effortsmarketing efforts Such acts as changing prices or increasing Such acts as changing prices or increasing

advertising to influence (confound) competitors’ test-advertising to influence (confound) competitors’ test-marketing results are ethically questionable.marketing results are ethically questionable.

Practical Experimental Design IssuesPractical Experimental Design Issues

• Basic versus Factorial Experimental DesignsBasic versus Factorial Experimental Designs Basic experimental designs – a single independent variable and Basic experimental designs – a single independent variable and

a single dependent variable.a single dependent variable. Factorial experimental design – allows for an investigation of the Factorial experimental design – allows for an investigation of the

interaction to two or more independent variables.interaction to two or more independent variables.

• Laboratory ExperimentLaboratory Experiment A situation in which the researcher has more complete control A situation in which the researcher has more complete control

over the research setting and extraneous variables.over the research setting and extraneous variables.

• Field ExperimentsField Experiments Research projects involving experimental manipulations that are Research projects involving experimental manipulations that are

implemented in a natural environment.implemented in a natural environment.

EXHIBIT 12.5EXHIBIT 12.5 The Artificiality of Laboratory versus Field ExperimentsThe Artificiality of Laboratory versus Field Experiments

Within-Subjects and Between-Subjects Within-Subjects and Between-Subjects DesignsDesigns

• Within-Subjects DesignWithin-Subjects Design Involves repeated measures because with each Involves repeated measures because with each

treatment the same subject is measured.treatment the same subject is measured.

• Between-Subjects DesignBetween-Subjects Design Each subject receives only one treatment Each subject receives only one treatment

combination.combination.

Usually advantageous although they are usually more Usually advantageous although they are usually more costly.costly.

Validity is usually higher.Validity is usually higher.

EXHIBIT 12.6EXHIBIT 12.6

Within- and Within- and Between-Between-Subjects Subjects DesignsDesigns

Issues of Experimental ValidityIssues of Experimental Validity

• Internal ValidityInternal Validity The extent that an experimental variable is truly The extent that an experimental variable is truly

responsible for any variance in the dependent responsible for any variance in the dependent variable.variable. Does the experimental manipulation truly cause changes in Does the experimental manipulation truly cause changes in

the specific outcome of interest?the specific outcome of interest?

• Manipulation ChecksManipulation Checks A validity test of an experimental manipulation to A validity test of an experimental manipulation to

make sure that the manipulation does produce make sure that the manipulation does produce differences in the independent variable.differences in the independent variable.

Extraneous Variables Affecting Internal Extraneous Variables Affecting Internal ValidityValidity

Internal Internal ValidityValidityInternal Internal ValidityValidity

MaturationMaturationMaturationMaturation

TestingTestingTestingTesting

InstrumentationInstrumentationInstrumentationInstrumentationSelectionSelectionSelectionSelection

MortalityMortalityMortalityMortality

HistoryHistoryHistoryHistory

Effects of Extraneous Variables on Effects of Extraneous Variables on ValidityValidity• History EffectHistory Effect

Occurs when some change other than the Occurs when some change other than the experimental treatment occurs during the course of experimental treatment occurs during the course of an experiment that affects the dependent variable.an experiment that affects the dependent variable.

Cohort EffectCohort Effect A change in the dependent variable that occurs because A change in the dependent variable that occurs because

members of one experimental group experienced different members of one experimental group experienced different historical situations than members of other experimental historical situations than members of other experimental groups.groups.

Effects of Extraneous Variables… Effects of Extraneous Variables… (cont’d)(cont’d)• Maturation EffectsMaturation Effects

Effects that are a function of time and the naturally Effects that are a function of time and the naturally occurring events that coincide with growth and occurring events that coincide with growth and experience.experience.

• Testing effectsTesting effects A nuisance effect occurring when the initial A nuisance effect occurring when the initial

measurement or test alerts or primes subjects in a measurement or test alerts or primes subjects in a way that affects their response to the experimental way that affects their response to the experimental treatments.treatments.

Effects of Extraneous Variables… Effects of Extraneous Variables… (cont’d)(cont’d)• Instrumentation EffectInstrumentation Effect

A change in the wording of questions, a change in A change in the wording of questions, a change in interviewers, or a change in other procedures causes interviewers, or a change in other procedures causes a change in the dependent variable.a change in the dependent variable.

• SelectionSelection The selection effect is a sample bias that results from The selection effect is a sample bias that results from

differential selection of respondents for the differential selection of respondents for the comparison groups, or a sample selection error.comparison groups, or a sample selection error.

• Mortality Effect (Sample Attrition)Mortality Effect (Sample Attrition) Occurs when some subjects withdraw from the Occurs when some subjects withdraw from the

experiment before it is completed.experiment before it is completed.

Extraneous VariablesExtraneous Variables

HistoryHistoryUncontrollable events occurring in Uncontrollable events occurring in the environment between before the environment between before and after measurementsand after measurements

MaturationMaturationChanges in subjects during the Changes in subjects during the course of the experimentcourse of the experiment

TestingTestingA before measure that alerts or A before measure that alerts or sensitizes subject to the nature of sensitizes subject to the nature of experiment or second measure. experiment or second measure.

A major employer closes its plant A major employer closes its plant in test market area.in test market area.

Subjects become tired during the Subjects become tired during the experiment.experiment.

A questionnaire about the A questionnaire about the traditional role of women traditional role of women triggers enhanced awareness of triggers enhanced awareness of females in an experiment.females in an experiment.

Extraneous Variable Example

Extraneous Variables (cont’d)Extraneous Variables (cont’d)

Instrument –Instrument –Changes in instrument result in Changes in instrument result in response biasresponse bias

SelectionSelectionSample selection error because of Sample selection error because of differential selection comparison differential selection comparison groups groups

MortalityMortalitySample attrition; some subjects Sample attrition; some subjects withdraw from experimentwithdraw from experiment

New questions about women are New questions about women are interpreted differently from earlier interpreted differently from earlier questions.questions.

Control group and experimental Control group and experimental group is self-selected group based group is self-selected group based on preference for soft drinkson preference for soft drinks

Subjects in one group of a hair Subjects in one group of a hair dying study marry rich widows and dying study marry rich widows and move to Floridamove to Florida

Extraneous Variable Example

Issues of Experimental Validity Issues of Experimental Validity (cont’d)(cont’d)• External ValidityExternal Validity

The accuracy with which experimental results can be The accuracy with which experimental results can be generalized beyond the experimental subjects.generalized beyond the experimental subjects. Student surrogates: Atypical?Student surrogates: Atypical?

• Trade-Offs Between Internal and External Trade-Offs Between Internal and External ValidityValidity Artificial laboratory experiments usually are high in Artificial laboratory experiments usually are high in

internal validity, while naturalistic field experiments internal validity, while naturalistic field experiments generally have less internal validity, but greater generally have less internal validity, but greater external validity.external validity.

LaboratoryExperiment

FieldExperiment

Artificial: Low RealismArtificial: Low RealismArtificial: Low RealismArtificial: Low Realism

Few ExtraneousFew ExtraneousVariablesVariables

High controlHigh controlHigh controlHigh control

Low CostLow CostLow CostLow Cost

Short DurationShort DurationShort DurationShort Duration

Subjects Aware ofSubjects Aware ofParticipationParticipation

Natural: High RealismNatural: High RealismNatural: High RealismNatural: High Realism

Many ExtraneousMany ExtraneousVariablesVariables

Low controlLow controlLow controlLow control

High CostHigh CostHigh CostHigh Cost

Long DurationLong DurationLong DurationLong Duration

Subjects Unaware ofSubjects Unaware ofParticipationParticipation

Laboratory versus Field ExperimentsLaboratory versus Field Experiments

Classification of Experimental DesignsClassification of Experimental Designs

• Basic Experimental DesignBasic Experimental Design An experimental design in which only one variable is An experimental design in which only one variable is

manipulated.manipulated.

• Diagramming Experimental Designs: SymbolsDiagramming Experimental Designs: Symbols

Examples of Quasi-Experimental Examples of Quasi-Experimental DesignsDesigns• Quasi-experimental DesignsQuasi-experimental Designs

Experimental designs that do not involve random Experimental designs that do not involve random allocation of subjects to treatment combinations.allocation of subjects to treatment combinations.

• One Shot Design (After Only):One Shot Design (After Only): XX OO11

• One Group Pretest–Posttest:One Group Pretest–Posttest: OO11 XX OO22

• Static Group Design:Static Group Design: ExperimentalExperimental XX OO11

ControlControl OO22

Alternative Experimental DesignsAlternative Experimental Designs

• PretestPretest––Posttest Control Group DesignPosttest Control Group Design(Before(Before–After with Control)–After with Control) ExperimentalExperimental R OR O11 X O X O22

ControlControl R OR O33 X O X O44

• Posttest Only Control GroupPosttest Only Control Group((After-Only with Control)After-Only with Control) ExperimentalExperimental R X OR X O11

ControlControl R OR O22

EXHIBIT 12.7EXHIBIT 12.7 Product Preference Measure in an ExperimentProduct Preference Measure in an Experiment

EXHIBIT 12.8EXHIBIT 12.8

Selected Time Selected Time Series OutcomesSeries Outcomes

Complex Experimental DesignsComplex Experimental Designs

Completely Completely Randomized Randomized

DesignDesign

Randomized Block Randomized Block DesignDesign

FactorialFactorial

Complex Experimental Designs Complex Experimental Designs (cont’d)(cont’d)• Completely Randomized DesignCompletely Randomized Design

An experimental design that uses a random process An experimental design that uses a random process to assign subjects (test units) to treatment levels to to assign subjects (test units) to treatment levels to investigate the effects of an experimental variable.investigate the effects of an experimental variable.

Complex Experimental Designs Complex Experimental Designs (cont’d)(cont’d)• Randomized Block DesignRandomized Block Design

An extension of the completely randomized design in An extension of the completely randomized design in which a single categorical extraneous variable that which a single categorical extraneous variable that might affect test units’ responses to the treatment is might affect test units’ responses to the treatment is identified and the effects of this variable are isolated identified and the effects of this variable are isolated by being blocked out.by being blocked out.

• Blocking VariableBlocking Variable A categorical variable that is expected to be A categorical variable that is expected to be

associated with different values of a dependent associated with different values of a dependent variable for each group. It effectively controls for an variable for each group. It effectively controls for an extraneous cause in experimental analysis.extraneous cause in experimental analysis.

EXHIBIT 12.9EXHIBIT 12.9 Randomized Block DesignRandomized Block Design

Complex Experimental Designs Complex Experimental Designs (cont’d)(cont’d)• Factorial DesignFactorial Design

An experiment that investigates the interaction of two or An experiment that investigates the interaction of two or more independent variables on a single dependent variable.more independent variables on a single dependent variable.

EXHIBIT 12.10EXHIBIT 12.10 Factorial Design—Salary and VacationFactorial Design—Salary and Vacation

Effects in Factorial DesignEffects in Factorial Design

• Main effectMain effect The influence of a single independent variable on a The influence of a single independent variable on a

dependent variable. dependent variable.

• Interaction effectInteraction effect The influence on a dependent variable by The influence on a dependent variable by

combinations of two or more independent variables.combinations of two or more independent variables.

Interaction occurs if the effect of one treatment differs Interaction occurs if the effect of one treatment differs at various levels of the other treatment.at various levels of the other treatment.

EXHIBIT 12.11EXHIBIT 12.11 A 2 A 2 ×× 2 Factorial Design That Illustrates the Effects of Sex and Ad 2 Factorial Design That Illustrates the Effects of Sex and Ad Content on BelievabilityContent on Believability

EXHIBIT 12.12EXHIBIT 12.12 Graphic Illustration of Interaction between Gender and Graphic Illustration of Interaction between Gender and Advertising CopyAdvertising Copy

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