Essay

For a two-tailed hypothesis test with 2424 degrees of freedom and an alpha level of .05.05, recall the critical values, explain the percentage of the distribution represented in each tail, and state the general rule for when a computed tt score leads to rejecting the null hypothesis.

Question: For a two-tailed hypothesis test with 2424 degrees of freedom and an alpha level of .05.05, recall the critical values, explain the percentage of the distribution represented in each tail, and state the general rule for when a computed tt score leads to rejecting the null hypothesis.

Sample answer: In a two-tailed test with 2424 degrees of freedom and an alpha level of .05.05, the critical values are 2.0642.064 and 2.064-2.064. Each critical value represents the boundary for the extreme outer regions, specifically the lowest 2.5%2.5\% of the distribution (below 2.064-2.064) and the highest 2.5%2.5\% of the distribution (above 2.0642.064). If a sample's computed tt score falls below 2.064-2.064 or above 2.0642.064, the resulting pp-value is less than .05.05, which provides sufficient statistical evidence to reject the null hypothesis.

Key points:

  • The critical values are 2.0642.064 and 2.064-2.064.
  • Each tail represents 2.5%2.5\% of the distribution.
  • A computed tt score falling below 2.064-2.064 or above 2.0642.064 is considered extreme.
  • An extreme tt score corresponds to a pp-value less than .05.05, resulting in rejecting the null hypothesis.

Rubric: To earn full credit, the response must correctly identify the critical values as 2.0642.064 and 2.064-2.064, note that each tail represents 2.5%2.5\% of the distribution, and state that the null hypothesis is rejected when a computed tt score is beyond these boundaries because the pp-value is less than .05.05.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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