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Explain why the assistant's assertion is incorrect, how the actual shape of the distribution is determined, and calculate the specific degrees of freedom value for this sample.
Case context: A health psychology researcher is comparing the average daily caffeine intake of a sample of 12 college students to a recommended limit using a one-sample -test. A student assistant suggests that the shape of the distribution is fixed and will be the same regardless of how many students are recruited for the study.
Question: Explain why the assistant's assertion is incorrect, how the actual shape of the distribution is determined, and calculate the specific degrees of freedom value for this sample.
Sample answer: The assistant's assertion is incorrect because the shape of a distribution is not fixed; instead, it is determined by the degrees of freedom (). For a one-sample -test, the degrees of freedom are calculated as the sample size minus one (). For this sample of 12 students, the degrees of freedom are . This value of determines the exact shape of the distribution used for the analysis.
Key points:
- The degrees of freedom () determine the exact shape of the distribution.
- The formula for a one-sample -test is .
- A sample size of results in , which dictates the distribution's shape.
Rubric: The response should explain that the shape of the distribution depends on the degrees of freedom rather than being static, state the formula , and correctly calculate that the degrees of freedom for this case study are .
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Research Methods in Psychology - 4th American Edition @ KPU
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