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A researcher argues that randomly assigning participants is the only valid way to evaluate an intervention. Using the principles of a pretest-posttest nonequivalent groups design, evaluate this claim. In one to three sentences, explain how this quasi-experimental design provides a strong alternative when random assignment is not possible.
Question: A researcher argues that randomly assigning participants is the only valid way to evaluate an intervention. Using the principles of a pretest-posttest nonequivalent groups design, evaluate this claim. In one to three sentences, explain how this quasi-experimental design provides a strong alternative when random assignment is not possible.
Sample answer: The researcher's claim is incorrect because a pretest-posttest nonequivalent groups design provides a robust alternative when random assignment is impossible. By introducing an initial baseline measurement, researchers can compare the pretest-to-posttest changes between a treatment group and a nonequivalent control group. This helps evaluate if the treated group demonstrated significantly greater improvement, effectively accounting for general maturation or historical effects.
Key points:
- Reject the claim that random assignment is the only valid method.
- Explain that the design compares pretest-to-posttest changes between a treatment and a nonequivalent control group.
- Note that this change-based comparison helps account for general maturation or historical effects.
Rubric: The response must reject the claim, noting that while random assignment is ideal, this quasi-experimental design is valid because the pretest-to-posttest change comparison accounts for maturation and historical effects.
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Research Methods in Psychology - 4th American Edition @ KPU
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