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Based on the concept of a planned analysis, explain why the psychologist's calculation of Cohen's dd qualifies as a planned analysis in this scenario.

Case context: A developmental psychologist sets up a study with the original hypothesis that toddlers who attend preschool will score higher on a standardized vocabulary test than those who stay at home. After collecting the data, the psychologist computes the group means, standard deviations, and a Cohen's dd to specifically evaluate this anticipated difference.

Question: Based on the concept of a planned analysis, explain why the psychologist's calculation of Cohen's dd qualifies as a planned analysis in this scenario.

Sample answer: The calculation of Cohen's dd qualifies as a planned analysis because the psychologist is conducting a statistical test to evaluate a specific difference between two conditions—preschool attendees scoring higher than non-attendees—that was explicitly expected in their original hypothesis prior to analyzing the data.

Key points:

  • The calculation of Cohen's dd tests an expected difference between the two toddler groups.
  • The difference between groups was explicitly predicted in the original hypothesis.
  • The analysis evaluates a pre-specified relationship rather than exploring unexpected findings.

Rubric: The response must explicitly connect the statistical test (Cohen's dd) to the original hypothesis established before data collection, demonstrating an understanding that planned analyses test explicitly anticipated relationships or differences.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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