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Based on the concepts of experimental design, explain how the student's initial plan differs from her revised plan in terms of independent variables, and summarize why her revised plan represents a more powerful methodological approach.
Case context: A cognitive psychology student wants to study the effects of caffeine on memory. Initially, she plans to use three different doses of caffeine (0mg, 100mg, and 200mg) as her only manipulation. However, she realizes that the time of day (morning versus evening) might also play a critical role in memory performance and decides to manipulate both factors together.
Question: Based on the concepts of experimental design, explain how the student's initial plan differs from her revised plan in terms of independent variables, and summarize why her revised plan represents a more powerful methodological approach.
Sample answer: The initial plan utilizes multiple levels (0mg, 100mg, 200mg) of a single independent variable (caffeine dose). The revised plan incorporates multiple independent variables (caffeine dose and time of day) within the exact same experiment. The revised plan is more powerful because it allows the student to answer a more sophisticated research question about how both variables impact memory, which cannot be fully addressed by studying caffeine in isolation.
Key points:
- The initial plan uses multiple levels of a single independent variable.
- The revised plan incorporates multiple independent variables within the same experiment.
- The revised plan enables answering more sophisticated research questions.
- It overcomes the limitations of studying variables in isolation.
Rubric: A correct response must distinguish between multiple levels of a single variable and the inclusion of multiple independent variables, demonstrating comprehension that the latter answers more complex research questions.
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Research Methods in Psychology - 4th American Edition @ KPU
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