Case Study

Assuming the researcher has set the significance level (α\alpha) at 0.050.05, what statistical decision should they make regarding the null hypothesis, and what conclusion should they draw about the relationship between physical activity and sleep quality? Justify your decision.

Case context: A psychologist is studying the correlation between daily physical activity (measured in minutes) and subjective sleep quality (measured on a scale from 1 to 10) among college students. After gathering data from a sample of 60 participants, the psychologist runs a Pearson correlation test in statistical software. The software output reports a computed pp-value of 0.0380.038.

Question: Assuming the researcher has set the significance level (α\alpha) at 0.050.05, what statistical decision should they make regarding the null hypothesis, and what conclusion should they draw about the relationship between physical activity and sleep quality? Justify your decision.

Sample answer: The researcher should reject the null hypothesis. Because the computed pp-value of 0.0380.038 is less than or equal to the pre-set alpha level of 0.050.05 (0.0380.050.038 \le 0.05), the result is statistically significant, indicating that there is a significant relationship between daily physical activity and subjective sleep quality in the population.

Key points:

  • Identify that the computed pp-value (0.0380.038) is less than or equal to the alpha level of 0.050.05.
  • Make the statistical decision to reject the null hypothesis.
  • Conclude that there is a statistically significant relationship between physical activity and sleep quality.

Rubric: Award full credit if the student: 1) states the decision is to reject the null hypothesis; 2) compares the computed pp-value (0.0380.038) to the alpha level (0.050.05) to justify the decision; and 3) concludes that there is a statistically significant relationship between physical activity and sleep quality.

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Updated 2026-05-26

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Research Methods in Psychology - 4th American Edition @ KPU

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