Case Study

Based on the principles of single-subject data analysis, identify the errors in the clinician's approach. Explain what primary analytical method the clinician should use instead and how they should view the role of the statistical t-test.

Case context: A clinician is testing a new cognitive training program with three individual stroke patients to improve their spatial memory. Rather than analyzing each patient's progress individually, the clinician averages the memory scores of the three patients at each weekly interval and runs a t-test to determine if there is a statistically significant change. A colleague suggests that this method does not follow the standard data analysis approach for single-subject research designs.

Question: Based on the principles of single-subject data analysis, identify the errors in the clinician's approach. Explain what primary analytical method the clinician should use instead and how they should view the role of the statistical t-test.

Sample answer: The clinician's approach is incorrect because single-subject data analysis relies on visual inspection of individual data rather than averaging across participants and using group-based inferential statistics like a t-test. Averaging the scores obscures individual trajectories. The clinician should graph each patient's data separately to visually detect changes and judge the treatment's effect. The t-test can only serve as a supplement, not a replacement for this visual inspection.

Key points:

  • Averaging across participants is incorrect because it hides individual data patterns.
  • Primary reliance on inferential statistics (t-test) is incorrect.
  • The primary method must be visual inspection of individual graphed data.
  • Statistical methods can supplement but cannot replace visual inspection.

Rubric: The student must show comprehension by diagnosing that group averaging and primary reliance on inferential statistics (t-test) are incorrect for single-subject designs. They must prescribe graphing and visual inspection of individual data, and state that the t-test is only supplemental.

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Updated 2026-05-26

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Research Methods in Psychology - 4th American Edition @ KPU

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