Case Study

Explain the difference in what the psychologist can expect regarding the average outcome for the new group of 300 clients versus the outcome for Leo individually. Explain the statistical reason for this difference in expectations.

Case context: A psychologist conducts a study with N=400N = 400 participants to evaluate a new therapeutic exercise. The study shows that the exercise has a small positive effect on average. The psychologist wants to recommend this exercise to a new group of 300 clients, and also to a specific individual client named Leo.

Question: Explain the difference in what the psychologist can expect regarding the average outcome for the new group of 300 clients versus the outcome for Leo individually. Explain the statistical reason for this difference in expectations.

Sample answer: The psychologist can expect a similar small positive average effect when applying the exercise to the group of 300 clients because it is a large group. However, for Leo individually, the psychologist cannot be certain of the outcome, which could be positive, small, or negative. This difference exists because the overall group average masks individual variation, meaning group-level generalizability does not guarantee a specific individual's response.

Key points:

  • Applying the treatment to another large group will likely result in a similar average effect.
  • Applying the treatment to a single individual (Leo) leads to an uncertain outcome.
  • Leo's outcome could be positive, small, or negative.
  • The statistical average masks varied individual responses.

Rubric: The response must demonstrate comprehension by predicting a similar average effect for the new group and noting the uncertainty (positive, small, or negative) for the individual client. It must identify that group averages mask individual differences, preventing certainty at the single-person level.

0

1

Updated 2026-05-27

Contributors are:

Who are from:

Tags

KPU

Research Methods in Psychology - 4th American Edition @ KPU

Related