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Based on the case context, justify the choice of research design by explaining why the psychologist's decision to collect multiple weekly measurements over a sixteen-week period is superior to using a simple before-and-after measurement. How does this methodology help in understanding the intervention's true impact?
Case context: A school psychologist is evaluating a new social skills training program designed to reduce weekly playground physical altercations. Instead of simply comparing the number of altercations from the single week before the program to the single week after, the psychologist records weekly altercations for eight weeks before implementing the program, and continues recording weekly for eight weeks after the program starts.
Question: Based on the case context, justify the choice of research design by explaining why the psychologist's decision to collect multiple weekly measurements over a sixteen-week period is superior to using a simple before-and-after measurement. How does this methodology help in understanding the intervention's true impact?
Sample answer: The psychologist is using an interrupted time-series design. Collecting weekly measurements for eight weeks before and eight weeks after the program allows the psychologist to establish a baseline of normal variation in playground altercations. If the psychologist only collected one measurement before and one after, they might mistake a temporary fluctuation or normal weekly variance for a program effect. By observing the entire time series, the psychologist can comprehend whether any reduction in altercations after the program's implementation is a genuine consequence of the social skills training or merely a reflection of normal, random week-to-week variations.
Key points:
- Identifies the scenario as an interrupted time-series design.
- Explains that multiple pre-treatment measurements establish a baseline of normal variation.
- Explains that a simple pretest-posttest design cannot rule out normal variation as a confounding explanation.
- Demonstrates comprehension of how the time-series pattern allows the researcher to isolate the true impact of the intervention.
Rubric: The response must identify the design as an interrupted time-series design, explain how the pre-treatment series establishes a baseline of normal variation, and explain why this rules out normal fluctuation as an explanation for the outcome better than a single pretest/posttest comparison.
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Research Methods in Psychology - 4th American Edition @ KPU
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