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Case Study

Explain why the researcher's prediction about 'Time of Day' is conceptually flawed based on the principles of factorial designs.

Case context: A researcher is conducting a factorial experiment to investigate how two different factors, 'Feedback Type' (Positive vs. Constructive) and 'Time of Day' (Morning vs. Afternoon), affect students' focus. After running the statistical analysis, the researcher finds a highly significant main effect of 'Feedback Type'. Based on this result, the researcher drafts a discussion section predicting that 'Time of Day' is also highly likely to show a significant main effect of similar magnitude.

Question: Explain why the researcher's prediction about 'Time of Day' is conceptually flawed based on the principles of factorial designs.

Sample answer: The researcher's prediction is flawed because main effects in a factorial design operate entirely independently of one another. The finding of a significant main effect for 'Feedback Type' has no bearing on and provides no predictive information regarding the presence, absence, or magnitude of a main effect for 'Time of Day'. Therefore, the researcher cannot use the strength of one main effect to forecast the outcome of another.

Key points:

  • Identify that the researcher's prediction is invalid because main effects are independent.
  • Explain that the main effect of 'Feedback Type' does not influence or predict the main effect of 'Time of Day'.
  • State that the presence, absence, or magnitude of a main effect for one variable cannot be inferred from the main effect of another variable in the same study.

Rubric: The answer should demonstrate comprehension of the independence of main effects by identifying that the researcher's attempt to predict the presence or magnitude of one main effect based on another is invalid. The student must explain that the two independent variables operate independently and that one main effect's outcome offers no information about the other.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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