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A researcher is using a single-subject design to evaluate an intervention designed to increase a participant's daily steps. During the baseline (control) phase, the highest recorded number of steps is 4,000. During the treatment phase, the participant records the following daily step counts across five sessions: 3,500, 4,200, 4,500, 3,800, and 5,000. Apply the definition of the Percentage of Non-Overlapping Data (PND) to calculate the PND for this study and explain what your result indicates about the treatment effect. Provide a concise analytical response.

Question: A researcher is using a single-subject design to evaluate an intervention designed to increase a participant's daily steps. During the baseline (control) phase, the highest recorded number of steps is 4,000. During the treatment phase, the participant records the following daily step counts across five sessions: 3,500, 4,200, 4,500, 3,800, and 5,000. Apply the definition of the Percentage of Non-Overlapping Data (PND) to calculate the PND for this study and explain what your result indicates about the treatment effect. Provide a concise analytical response.

Sample answer: The most extreme response in the control condition is 4,000 steps. In the treatment condition, there are 5 total responses, and 3 of them (4,200, 4,500, and 5,000) are more extreme (greater) than the highest baseline response. Therefore, the PND is 60%60\% (3/5×1003/5 \times 100). This indicates a moderate treatment effect, as a greater percentage of non-overlapping data points to a stronger effect.

Key points:

  • Identifies the most extreme control response as 4,000 steps.
  • Counts exactly 3 treatment responses that are more extreme than the control.
  • Calculates the PND correctly as 60%60\%.
  • Explains that this percentage indicates a positive treatment effect based on the principle that greater PND means a stronger effect.

Rubric: Full credit requires correctly identifying the most extreme baseline value, counting the correct number of more extreme treatment values, calculating the correct percentage, and stating what the result implies about the 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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