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Case Study

Based on the provided data, calculate the Percentage of Non-Overlapping Data (PND) for both patients. Diagnose which patient demonstrated a stronger treatment effect from the intervention and justify your decision using the definition of PND.

Case context: A clinical psychologist is comparing the effectiveness of a new behavioral intervention for two different patients using a single-subject design aimed at decreasing aggressive outbursts. For Patient A, the most extreme (lowest) number of outbursts in the control condition is 3. In the treatment condition, Patient A has 10 sessions, with 8 sessions having fewer than 3 outbursts. For Patient B, the lowest number of outbursts in the control condition is 2. In the treatment condition, Patient B has 10 sessions, with 9 sessions having fewer than 2 outbursts.

Question: Based on the provided data, calculate the Percentage of Non-Overlapping Data (PND) for both patients. Diagnose which patient demonstrated a stronger treatment effect from the intervention and justify your decision using the definition of PND.

Sample answer: For Patient A, 8 out of 10 treatment sessions are more extreme than the control condition, resulting in a PND of 80%80\%. For Patient B, 9 out of 10 treatment sessions are more extreme than the control, yielding a PND of 90%90\%. Patient B demonstrated a stronger treatment effect because a greater percentage of non-overlapping data indicates a stronger treatment effect.

Key points:

  • Calculates Patient A's PND as 80%80\%.
  • Calculates Patient B's PND as 90%90\%.
  • Concludes that Patient B shows the stronger treatment effect.
  • Justifies the conclusion by stating that a higher PND corresponds to a stronger treatment effect.

Rubric: The response must accurately calculate the PND for both Patient A and Patient B, correctly identify Patient B as having the stronger effect, and explicitly link this to the concept that a higher PND equals a stronger treatment effect.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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