Case Study

Explain why critics of null hypothesis testing would argue that the psychologist's conclusion is unsupported based solely on rejecting the null hypothesis. How does the concept of "uninformativeness" help diagnose the limitation of the psychologist's finding?

Case context: A psychologist studies the correlation between sleep duration and academic performance in college students. After collecting data, the psychologist rejects the null hypothesis of precisely zero relationship (r=0.00r = 0.00) with a statistically significant result. Based on this, the psychologist concludes that sleep duration has a substantial and practically important effect on students' grades.

Question: Explain why critics of null hypothesis testing would argue that the psychologist's conclusion is unsupported based solely on rejecting the null hypothesis. How does the concept of "uninformativeness" help diagnose the limitation of the psychologist's finding?

Sample answer: Critics would argue that the psychologist's conclusion is unsupported because rejecting the null hypothesis only confirms that the correlation is not exactly zero (r0.00r \neq 0.00). Since a relationship of precisely zero is never literally true in reality, rejecting the null hypothesis is a trivial finding. It does not provide any precise information about the actual strength or nature of the relationship, meaning the psychologist cannot justify the claim that sleep has a 'substantial' or 'important' effect based only on a significant p-value.

Key points:

  • Rejecting the null hypothesis only confirms that some nonzero relationship exists (r0.00r \neq 0.00).
  • A null hypothesis of precisely zero relationship is never literally true in the real world.
  • Rejecting the null hypothesis does not provide precise information about the actual strength or nature of the phenomenon, making claims of a substantial effect unsupported.

Rubric: To receive full credit, the response must: 1. Explain that rejecting the null hypothesis only tells the psychologist that the correlation is not exactly zero (r0.00r \neq 0.00). 2. Explain that a null hypothesis of precisely zero is never literally true in the real world. 3. Justify why this limitation means the psychologist cannot conclude the effect is 'substantial' or 'important' (the test does not measure the actual strength or nature of the relationship).

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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