Chapter 8
Experimental Research
Chapter 7
Conducting & Reading Research
Baumgartner et al
Steps in Experimental Research
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
Stating the research problem
Determining if experimental approach is appropriate
Specifying the independent variable(s)
Specifying all potential dependent variables
Stating the tentative hypotheses
Determining availability of measures for potential
dependent variables
Pausing to consider success potential of the research
Identifying full potential of intervening variables
Making a formal statement of the research hypotheses
Designing the experiment
Making final estimate of success potential of the study
Conducting the study as planned in steps 1 through 11
Analyzing the data
Preparing a research report
Chapter 7
Conducting & Reading Research
Baumgartner et al
Internal and External Validity
•
validity: How valid are the
findings within the study?
•
validity: How much can the
findings be inferred or generalized to
other populations, settings, or
treatments?
• Must have good internal validity to
have good external validity, but
doesn’t guarantee good external
validity.
Chapter 7
Conducting & Reading Research
Baumgartner et al
Threats to Internal Validity
•
•
•
•
•
•
•
•
History
Maturation
Testing
Instrumentation
Statistical Regression
Selection
Experimental Mortality
Interaction of Selection and
Maturation or History
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Conducting & Reading Research
Baumgartner et al
Threats to External Validity
• Interaction Effect of Testing
• Interaction Effects of Selection Bias
and Experimental Treatment
• Reactive Effects of Experimental
Setting
• Multiple-Treatment Interference
Chapter 7
Conducting & Reading Research
Baumgartner et al
Types of Designs
•
designs: variety of ways a research
study may be structured or
conducted
Three main types of designs
1.
experimental designs
2.
experimental designs
3.
designs
Chapter 7
Conducting & Reading Research
Baumgartner et al
True experimental design
• “
”
• random sampling of participants,
random assignment to groups, all
threats to internal validity controlled
• Not always possible
Chapter 7
Conducting & Reading Research
Baumgartner et al
Quasi-experimental design
• “
”
• Lack either random sampling or
random assignment
• Controls threats to validity of
history, maturation, testing,
instrumentation, selection, and
experimental mortality
Chapter 7
Conducting & Reading Research
Baumgartner et al
Preexperimental designs
• “
”
• no random sampling of participants,
limited groups, control few threats to
validity
Chapter 7
Conducting & Reading Research
Baumgartner et al
Methods of Control
• physical manipulation: researcher
controls all aspects of participants’
environment and experience
• selective manipulation
• statistical techniques
Chapter 7
Conducting & Reading Research
Baumgartner et al
Common Sources of Error
• Hawthorne Effect: participants in an experiment may
perform differently because they know they’re in a study
• Placebo Effect: participants receiving treatment believe the
treatment will have an effect (use single-blind approach)
• “John Henry” Effect: Control group might try harder in
attempt to outperform experimental group
• Rating Effects: halo effect, overrater or underrater error,
central tendency error
• Experimental Bias Effect: try to control using double-blind
approach
• Participant-Researcher Interaction Effect: Gender issues,
age, etc.
• Post Hoc Error: Assuming cause-and-effect relationship
where one does not exist
Chapter 7
Conducting & Reading Research
Baumgartner et al