Case Study

Explain how Dr. Miller should apply the logic of null hypothesis testing to her study. Specifically, describe the initial assumption she must make, what probability she needs to determine, and the two possible logical conclusions she could draw based on that probability.

Case context: Dr. Miller is investigating whether a new mindfulness training program improves focus in college students. After measuring a sample of students, she finds a positive relationship between mindfulness practice and focus. She now wants to evaluate this relationship using the formal process of null hypothesis testing.

Question: Explain how Dr. Miller should apply the logic of null hypothesis testing to her study. Specifically, describe the initial assumption she must make, what probability she needs to determine, and the two possible logical conclusions she could draw based on that probability.

Sample answer: Dr. Miller must start by temporarily assuming that the null hypothesis is true, which means there is no relationship between mindfulness training and focus in the population. Next, she must determine the probability of obtaining her sample's positive relationship under this assumption. If she finds that this sample result is extremely unlikely under a true null hypothesis, she will reject the null hypothesis in favor of the alternative hypothesis. If the result is not extremely unlikely, she will retain the null hypothesis.

Key points:

  • Assume that the mindfulness program has no relationship to focus in the population.
  • Determine the probability of obtaining the observed sample relationship given a true null hypothesis.
  • Reject the null hypothesis if the sample relationship is extremely unlikely.
  • Retain the null hypothesis if the sample relationship is not extremely unlikely.

Rubric: Grading Rubric: - Identifies that Dr. Miller must assume no relationship exists in the population (null hypothesis is true). - Explains that she must determine the probability of her sample's positive relationship occurring under that assumption. - Explains the decision rules: rejecting the null if the sample result is extremely unlikely, and retaining it if not.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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