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
14-5
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
14-6
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
14-7
8. Ways to Assign Subjects
• Random Assignment
• Matching Assignment
– Quota matrix
14-8
9. Does a Measure Accomplish
What it Claims?
• Internal validity
• External validity
14-9
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
14-11
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
14-13
14. Preexperimental Designs
• One-shot case study
• One-group pretest-posttest design
• Static group comparison
14-14
15. True Experimental Designs
• Pretest-posttest control group design
• Posttest-only control group design
14-15
17. Field Experiments:
Quasi- or Semi-Experiments
• Non Equivalent Control Group Design
• Separate Sample Pretest-Posttest
Design
• Group Time Series Design
14-17