Essay

Based on the provided distribution example, explain how the degrees of freedom are calculated for a sample of 2525 individuals. Then, state how a researcher defines an "extreme" tt score in both directions to find the proportion of expected scores that make up the pp-value.

Question: Based on the provided distribution example, explain how the degrees of freedom are calculated for a sample of 2525 individuals. Then, state how a researcher defines an "extreme" tt score in both directions to find the proportion of expected scores that make up the pp-value.

Sample answer: For a sample of 2525 individuals, the degrees of freedom are calculated as 2424 (n1n - 1). When defining extreme in both directions, the pp-value is determined by combining the proportion of expected tt scores in the distribution that are 1.501.50 or greater with the proportion of expected tt scores that are 1.50-1.50 or lower, which sum to a final combined proportion of .14.14.

Key points:

  • Identify that a sample of 2525 individuals corresponds to 2424 degrees of freedom.
  • Explain that the pp-value combines proportions from both the positive and negative ends of the distribution.
  • Recall that the proportion of expected scores at or above 1.501.50 and at or below 1.50-1.50 is combined.
  • State that the final combined proportion is .14.14.

Rubric: Full credit requires identifying that 2525 individuals corresponds to 2424 degrees of freedom, explaining that "extreme in both directions" means combining the proportion of scores at or above 1.501.50 and at or below 1.50-1.50, and recalling that the combined proportion equals .14.14.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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