Case Study

Diagnose the statistical error in the lead author's conclusion. Based on your understanding of pp-values and replication, what must the researchers consider before estimating the true likelihood of replication?

Case context: A research team conducts an experiment on a novel cognitive behavioral therapy technique for generalized anxiety disorder. They analyze their data and find a statistically significant reduction in anxiety scores with a pp-value of .02.02. In their discussion section, the lead author writes, 'Given our pp-value of .02.02, we can be confident there is a 98%98\% probability that other clinics will successfully replicate our significant results if they use the exact same therapy protocol.'

Question: Diagnose the statistical error in the lead author's conclusion. Based on your understanding of pp-values and replication, what must the researchers consider before estimating the true likelihood of replication?

Sample answer: The lead author has fallen for the misconception that the probability of replication is equal to 1p1 - p. Calculating 1.021 - .02 to get 98%98\% is an incorrect way to determine replication chances. To properly estimate the likelihood of a successful replication, the researchers must consider the statistical power of the planned replication study, which is typically much more demanding and is not directly provided by the original study's pp-value alone.

Key points:

  • Identify that the author incorrectly used the 1p1 - p formula to find replication probability.
  • Diagnose the 98%98\% replication claim as a statistical misconception.
  • State that a low pp-value (.02.02) is not a guarantee of future replication.
  • Explain that actual replication probability requires adequate statistical power.

Rubric: Full credit is awarded if the student identifies the 1p1 - p fallacy and states that statistical power must be considered to estimate actual replication probability.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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