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Case Study

Based on the definition of a main effect, explain what the main effect of 'Sleep Deprivation' would represent in this specific study and how the researcher would determine its overall influence from the data.

Case context: A researcher is conducting a factorial design experiment examining the effects of two independent variables: 'Sleep Deprivation' (None vs. 24 Hours) and 'Caffeine Intake' (0 mg vs. 200 mg) on a dependent variable of cognitive test scores.

Question: Based on the definition of a main effect, explain what the main effect of 'Sleep Deprivation' would represent in this specific study and how the researcher would determine its overall influence from the data.

Sample answer: The main effect of Sleep Deprivation would represent its overall influence on cognitive test scores. To determine this, the researcher would average the cognitive test scores for each level of sleep deprivation (None and 24 Hours) across all levels of the other independent variable, which is Caffeine Intake.

Key points:

  • The main effect of Sleep Deprivation represents its overall influence on the cognitive test scores.
  • It is determined by averaging the scores for each sleep deprivation condition.
  • The averaging must occur across all levels of the other independent variable, Caffeine Intake.

Rubric: The answer should demonstrate an understanding that the main effect isolates one variable by averaging across the other. It must specifically state that the overall influence of sleep deprivation is found by averaging across the levels of caffeine intake.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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