Case Study

Based on your understanding of the Percentage of Non-Overlapping Data (PND) from the study of Robbie's study time, how should the psychologist calculate the PND for this reading intervention? Determine the PND value and explain what this value implies about the treatment's effectiveness.

Case context: A school psychologist is evaluating a new intervention designed to increase a student's reading time. Following the single-subject design logic used by Hall and colleagues in their research on Robbie's study time, the psychologist establishes a baseline and records the highest baseline reading time as 12 minutes. During the treatment phase, the psychologist records the following reading times: 15 minutes, 13 minutes, 16 minutes, and 14 minutes.

Question: Based on your understanding of the Percentage of Non-Overlapping Data (PND) from the study of Robbie's study time, how should the psychologist calculate the PND for this reading intervention? Determine the PND value and explain what this value implies about the treatment's effectiveness.

Sample answer: To calculate the PND, the psychologist needs to compare the treatment measurements to the highest baseline measurement, which is 12 minutes. The treatment measurements are 15, 13, 16, and 14 minutes. Since all 4 treatment measurements are strictly greater than the baseline maximum of 12 minutes, the percentage of non-overlapping data is 100%. Based on Robbie's study time example, a PND of 100% indicates that all treatment responses are more extreme than the baseline responses, representing a very strong treatment effect.

Key points:

  • Identify 12 minutes as the highest baseline measurement.
  • Show that all treatment data points (15, 13, 16, 14) exceed 12 minutes.
  • Compute the resulting PND as 100%.
  • Explain that 100% PND indicates a very strong treatment effect.

Rubric: The response should: 1) Correctly identify 12 minutes as the baseline maximum; 2) Compare all treatment measurements (15, 13, 16, 14) to the baseline maximum and confirm they are all greater; 3) Calculate the PND as 100%; and 4) Explain that a 100% PND represents a very strong 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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