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Based on the provided case, explain how the psychologist should use the alpha (α\alpha) criterion to interpret her pp value of .03.03. What does this mean for her decision regarding the null hypothesis, and why?

Case context: A clinical psychologist measures the effectiveness of a new mindfulness app on reducing anxiety in college students. Before gathering data, they set their significance threshold at the standard alpha (α\alpha) level. After running their statistical analysis, they find that the probability of obtaining their sample result if the treatment had no effect (pp value) is .03.03.

Question: Based on the provided case, explain how the psychologist should use the alpha (α\alpha) criterion to interpret her pp value of .03.03. What does this mean for her decision regarding the null hypothesis, and why?

Sample answer: The psychologist should compare her obtained pp value of .03.03 to the standard predefined alpha (α\alpha) criterion of .05.05. Because .03.03 is less than .05.05, the sample result is considered unlikely enough to have occurred by chance under the null hypothesis. Therefore, she should reject the null hypothesis.

Key points:

  • Compare the obtained pp value of .03.03 to the standard alpha criterion of .05.05
  • State that .03.03 is lower than the .05.05 threshold
  • Conclude that the psychologist must reject the null hypothesis

Rubric: Grading Rubric: - 1 point: Identifies the standard alpha criterion is .05.05 (or 5%5\%). - 1 point: Compares the pp value of .03.03 to the alpha threshold of .05.05 and notes that it is lower. - 1 point: Explains that this means the result is unlikely enough to reject the null hypothesis.

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Updated 2026-05-26

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Research Methods in Psychology - 4th American Edition @ KPU

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