This document discusses experimentation in research. It covers key topics such as variables in experiments, advantages and disadvantages of experiments, the experimentation process, ways to assign subjects, threats to internal and external validity, experimental designs including preexperimental, true experimental, and field experiments. Specific experimental designs mentioned include randomized block design, Latin square, and factorial design.

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2. Part Three
SOURCES AND
COLLECTION OF DATA
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McGraw-Hill/Irwin © 2003 The McGraw-Hill Companies, Inc.,All Rights Reserved.

3. Chapter Fourteen
EXPERIMENTATION
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4. Variables in Experiments
• Independent variables
• Dependent variables
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5. Advantages of an Experiment?
• Researcher’s ability to manipulate the
independent variable
• Contamination from extraneous
variables can be controlled more
efficiently
• Convenience
• Cost
• Replication
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6. Disadvantages of Experiments
• Artificiality of the laboratory
• Generalization from nonprobability
samples
• Larger budgets needed
• Restricted to problems of the present or
immediate future
• Ethical limits to manipulation of people
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7. Experimentation Process
• Select relevant variables
• Specify the treatment levels
• Control the experimental environment
• Choose the experimental design
• Select and assign the participants
• Pilot-test, revise, and test
• Analyze the data
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8. Ways to Assign Subjects
• Random Assignment
• Matching Assignment
– Quota matrix
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9. Does a Measure Accomplish
What it Claims?
• Internal validity
• External validity
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10. Threats to Internal Validity
• History • Selection
• Maturation • Statistical
• Testing Regression
• Instrumentation • Experimental
Mortality
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11. Threats to External Validity
• The Reactivity of Testing on X
• Interaction of Selection and X
• Other Biasing Effects on X
– Artificial setting of testing
– Respondents knowledge of testing
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12. Experimental Designs
• Preexperimental designs
• True experimental designs
• Field experiments
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13. Design Symbols
X the introduction of an experimental
stimulus to the participant
0 a measure or observation activity
R an indication that sample units have
been randomly assigned
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14. Preexperimental Designs
• One-shot case study
• One-group pretest-posttest design
• Static group comparison
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15. True Experimental Designs
• Pretest-posttest control group design
• Posttest-only control group design
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16. Operational Extensions of True Designs
• Completely randomized designs
• Randomized block design
• Latin square
• Factorial design
• Covariance analysis
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17. Field Experiments:
Quasi- or Semi-Experiments
• Non Equivalent Control Group Design
• Separate Sample Pretest-Posttest
Design
• Group Time Series Design
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