Short Answer

Suppose a researcher obtains a tt score of 1.501.50 based on a sample of 2525 but defines 'extreme' as only being far from zero in the positive direction. Using the symmetric nature of the tt distribution and the two-tailed pp-value of .14.14, calculate the new one-tailed pp-value and explain your calculation in one to three sentences.

Question: Suppose a researcher obtains a tt score of 1.501.50 based on a sample of 2525 but defines 'extreme' as only being far from zero in the positive direction. Using the symmetric nature of the tt distribution and the two-tailed pp-value of .14.14, calculate the new one-tailed pp-value and explain your calculation in one to three sentences.

Sample answer: The new one-tailed pp-value would be .07.07. Because the tt distribution is symmetric, the two-tailed pp-value of .14.14 is divided equally between the upper tail (1.501.50 or above) and the lower tail (1.50-1.50 or below), meaning each tail contains a proportion of .07.07.

Key points:

  • Calculate the one-tailed pp-value as .07.07.
  • Apply the symmetric property of the tt distribution.
  • Explain that the two-tailed value is split equally between the upper and lower tails.

Rubric: The student must apply the concept of symmetry to calculate a one-tailed pp-value of .07.07 and explain that the two-tailed probability is split equally between the two tails.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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