ZIKMUND BABIN
CARR GRIFFIN
BUSINESS
MARKET
RESEARCH
EIGHTH EDITION
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website, in whole or in part.
Chapter 12
Experimental
Research
LEARNING OUTCOMES
After studying this chapter, you should be able to
1. Identify the independent variable, dependent
variable, and construct a valid simple
experiment to assess a cause and effect
relationship
2. Understand and minimize experimental error
3. Know ways of minimizing experimental
demand characteristics
4. Avoid unethical experimental practices
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website, in whole or in part.
12–2
LEARNING OUTCOMES (cont’d)
After studying this chapter, you should be able to
5. Understand the advantages of a betweensubjects experimental design
6. Weigh the trade-off between internal and
external validity
7. Use manipulations to implement a completely
randomized experimental design, a
randomized-block design, and a factorial
experimental design
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website, in whole or in part.
12–3
Creating an Experiment
• Subjects
 The sampling units for an experiment, usually human
respondents who provide measures based on the
experimental manipulation.
• Independent Variables
 Experimental conditions

One of the possible levels of an experimental (independent)
variable manipulation.
 Blocking variables
Variables included in the statistical analysis as a way of
controlling or accounting for variance due to that variable:
 Categorical variables

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website, in whole or in part.
12–4
EXHIBIT 12.1
Experimental Conditions in Self-Efficacy Experiment
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12–5
Creating an Experiment (cont’d)
• Main Effect
 The experimental difference in dependent variable
means between the different levels of any single
experimental variable.
• Interaction Effect
 Differences in dependant variable means due to a
specific combination of independent variables.
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website, in whole or in part.
12–6
EXHIBIT 12.2
Job Satisfaction Means in Self-Efficacy Experiment
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website, in whole or in part.
12–7
EXHIBIT 12.3
Experimental Graph Showing Results within Each Condition
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12–8
Designing an Experiment to Minimize
Experimental Error
• Manipulation of the Independent Variable
 Experimental treatment: the way an experimental
variable is manipulated.

Categorical variables: described by class or quality

Continuous variables: described by quantity (level)
 Experimental Group

A group of subjects to whom an experimental treatment is
administered.
 Control Group

A group of subjects to whom no experimental treatment is
administered.
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website, in whole or in part.
12–9
Designing an Experiment (cont’d)
• More than One Independent Variable
 Cell: a specific treatment combination associated with
an experimental group.
 Computation
of the number of cells in an
experiment:
K = (T1)(T2)..(Tm)
• Repeated Measures
 Experiments in which an individual subject is exposed
to more than one level of an experimental treatment.
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website, in whole or in part.
12–10
Designing an Experiment (cont’d)
• Selection and Measurement of the Dependent
Variable
 Selecting dependent variables that are relevant and
truly represent an outcome of interest is crucial.
 Choosing the right dependent variable is part of the
problem definition process.

Thorough problem definition will help the researcher select
the most important dependent variable(s).
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website, in whole or in part.
12–11
Designing an Experiment (cont’d)
• Selection and Assignment of Test Units
 Test units: the subjects or entities whose responses
to treatment are measured or observed.
• Sample Selection And Random Sampling Errors
 Systematic or nonsampling error

Subject selection, experimental design, and unrecognized
extraneous variables
 Overcoming sampling errors
Randomization
 Matching
 Control over extraneous variables

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scanned, copied or duplicated, or posted to a publically accessible
website, in whole or in part.
12–12
Designing an Experiment (cont’d)
• Sample Selection And Random Sampling Errors
 Experimental Confound
When there is an alternative explanation beyond the
experimental variables for any observed differences in the
dependent variable.
 Once a potential confound is identified, the validity of the
experiment is severely questioned.

 Extraneous variables

Variables that naturally exist in the environment that may
have some systematic effect on the dependent variable.
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website, in whole or in part.
12–13
Demand Characteristics
• Demand Characteristic
 An experimental design element or procedure that
unintentionally provides subjects with hints about the
research hypothesis.
• Demand Effect
 Occurs when demand characteristics actually affect
the dependent variable.
• Hawthorne Effect
 People will perform differently from normal when they
know they are experimental subjects.
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website, in whole or in part.
12–14
Reducing Demand Effects
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12–15
Establishing Control
• Constancy of Conditions
 Subjects in all experimental groups are exposed to
identical conditions except for the differing
experimental treatments.
• Counterbalancing
 Attempts to eliminate the confounding effects of order
of presentation by varying the order of presentation
(exposure) of treatments to subject groups.
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scanned, copied or duplicated, or posted to a publically accessible
website, in whole or in part.
12–16
Ethical Issues in Experimentation
• Debriefing experimental subjects
 Communicating the purpose of the experiment
 Explaining the researcher’s hypotheses
• Attempts to interfere with a competitor’s testmarketing efforts
 Such acts as changing prices or increasing
advertising to influence (confound) competitors’ testmarketing results are ethically questionable.
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scanned, copied or duplicated, or posted to a publically accessible
website, in whole or in part.
12–17
Practical Experimental Design Issues
• Basic versus Factorial Experimental Designs
 Basic experimental designs – a single independent variable and
a single dependent variable.
 Factorial experimental design – allows for an investigation of the
interaction to two or more independent variables.
• Laboratory Experiment
 A situation in which the researcher has more complete control
over the research setting and extraneous variables.
• Field Experiments
 Research projects involving experimental manipulations that are
implemented in a natural environment.
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scanned, copied or duplicated, or posted to a publically accessible
website, in whole or in part.
12–18
EXHIBIT 12.5
The Artificiality of Laboratory versus Field Experiments
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12–19
Within-Subjects and Between-Subjects
Designs
• Within-Subjects Design
 Involves repeated measures because with each
treatment the same subject is measured.
• Between-Subjects Design
 Each subject receives only one treatment
combination.
 Usually advantageous although they are usually more
costly.
 Validity is usually higher.
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website, in whole or in part.
12–20
EXHIBIT 12.6
Within- and
BetweenSubjects
Designs
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12–21
Issues of Experimental Validity
• Internal Validity
 The extent that an experimental variable is truly
responsible for any variance in the dependent
variable.

Does the experimental manipulation truly cause changes in
the specific outcome of interest?
• Manipulation Checks
 A validity test of an experimental manipulation to
make sure that the manipulation does produce
differences in the independent variable.
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website, in whole or in part.
12–22
Extraneous Variables Affecting Internal Validity
Maturation
History
Mortality
Internal
Validity
Selection
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Testing
Instrumentation
12–23
Effects of Extraneous Variables on Validity
• History Effect
 Occurs when some change other than the
experimental treatment occurs during the course of
an experiment that affects the dependent variable.
 Cohort Effect

A change in the dependent variable that occurs because
members of one experimental group experienced different
historical situations than members of other experimental
groups.
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12–24
Effects of Extraneous Variables… (cont’d)
• Maturation Effects
 Effects that are a function of time and the naturally
occurring events that coincide with growth and
experience.
• Testing effects
 A nuisance effect occurring when the initial
measurement or test alerts or primes subjects in a
way that affects their response to the experimental
treatments.
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scanned, copied or duplicated, or posted to a publically accessible
website, in whole or in part.
12–25
Effects of Extraneous Variables… (cont’d)
• Instrumentation Effect
 A change in the wording of questions, a change in
interviewers, or a change in other procedures causes
a change in the dependent variable.
• Selection
 The selection effect is a sample bias that results from
differential selection of respondents for the
comparison groups, or a sample selection error.
• Mortality Effect (Sample Attrition)
 Occurs when some subjects withdraw from the
experiment before it is completed.
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12–26
Extraneous Variables
Extraneous Variable
Example
History
Uncontrollable events occurring in
the environment between before
and after measurements
A major employer closes its plant
in test market area.
Maturation
Changes in subjects during the
course of the experiment
Subjects become tired during the
experiment.
Testing
A before measure that alerts or
sensitizes subject to the nature of
experiment or second measure.
A questionnaire about the
traditional role of women
triggers enhanced awareness of
females in an experiment.
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website, in whole or in part.
12–27
Extraneous Variables (cont’d)
Extraneous Variable
Instrument –
Changes in instrument result in
response bias
Example
New questions about women are
interpreted differently from earlier
questions.
Selection
Sample selection error because of
differential selection comparison
groups
Control group and experimental
group is self-selected group based
on preference for soft drinks
Mortality
Sample attrition; some subjects
withdraw from experiment
Subjects in one group of a hair
dying study marry rich widows and
move to Florida
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scanned, copied or duplicated, or posted to a publically accessible
website, in whole or in part.
12–28
Issues of Experimental Validity (cont’d)
• External Validity
 The accuracy with which experimental results can be
generalized beyond the experimental subjects.

Student surrogates: Atypical?
• Trade-Offs Between Internal and External
Validity
 Artificial laboratory experiments usually are high in
internal validity, while naturalistic field experiments
generally have less internal validity, but greater
external validity.
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scanned, copied or duplicated, or posted to a publically accessible
website, in whole or in part.
12–29
Laboratory versus Field Experiments
Laboratory
Experiment
Field
Experiment
Artificial: Low Realism
Natural: High Realism
Few Extraneous
Variables
Many Extraneous
Variables
High control
Low control
Low Cost
High Cost
Short Duration
Long Duration
Subjects Aware of
Participation
Subjects Unaware of
Participation
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website, in whole or in part.
12–30
Classification of Experimental Designs
• Basic Experimental Design
 An experimental design in which only one variable is
manipulated.
• Diagramming Experimental Designs: Symbols
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12–31
Examples of Quasi-Experimental Designs
• Quasi-experimental Designs
 Experimental designs that do not involve random
allocation of subjects to treatment combinations.
• One Shot Design (After Only):
X O1
• One Group Pretest–Posttest:
O1 X O2
• Static Group Design: Experimental
X O1
Control
O2
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12–32
Alternative Experimental Designs
• Pretest–Posttest Control Group Design
(Before–After with Control)
 Experimental
 Control
R O 1 X O2
R O 3 X O4
• Posttest Only Control Group
(After-Only with Control)
 Experimental
 Control
R X O1
R O2
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12–33
EXHIBIT 12.7
Product Preference Measure in an Experiment
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12–34
EXHIBIT 12.8
Selected Time
Series Outcomes
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12–35
Complex Experimental Designs
Completely
Randomized
Design
Randomized Block
Design
Factorial
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12–36
Complex Experimental Designs (cont’d)
• Completely Randomized Design
 An experimental design that uses a random process
to assign subjects (test units) to treatment levels to
investigate the effects of an experimental variable.
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12–37
Complex Experimental Designs (cont’d)
• Randomized Block Design
 An extension of the completely randomized design in
which a single categorical extraneous variable that
might affect test units’ responses to the treatment is
identified and the effects of this variable are isolated
by being blocked out.
• Blocking Variable
 A categorical variable that is expected to be
associated with different values of a dependent
variable for each group. It effectively controls for an
extraneous cause in experimental analysis.
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12–38
EXHIBIT 12.9
Randomized Block Design
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12–39
Complex Experimental Designs (cont’d)
• Factorial Design
 An experiment that investigates the interaction of two
or more independent variables on a single dependent
variable.
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website, in whole or in part.
12–40
EXHIBIT 12.10
Factorial Design—Salary and Vacation
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12–41
Effects in Factorial Design
• Main effect
 The influence of a single independent variable on a
dependent variable.
• Interaction effect
 The influence on a dependent variable by
combinations of two or more independent variables.
 Interaction occurs if the effect of one treatment differs
at various levels of the other treatment.
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12–42
EXHIBIT 12.11
A 2 × 2 Factorial Design That Illustrates the Effects of Sex and Ad Content
on Believability
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12–43
EXHIBIT 12.12
Graphic Illustration of Interaction between Gender and Advertising Copy
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12–44