Case Study

Explain how Dr. Aris would use G*Power to determine his required sample size. In your explanation, identify what specific target power level he should aim for and how the program uses his inputs to calculate the sample size.

Case context: Dr. Aris is planning a study to test whether a new stress-reduction exercise has an effect on student anxiety levels. He knows manual calculation of statistical power is complex, so he decides to use G*Power to determine the necessary sample size. He expects a moderate relationship strength based on previous literature and plans to use a standard α\alpha level.

Question: Explain how Dr. Aris would use G*Power to determine his required sample size. In your explanation, identify what specific target power level he should aim for and how the program uses his inputs to calculate the sample size.

Sample answer: Dr. Aris will input his expected moderate relationship strength, his chosen α\alpha level, and a target power level of .80.80 into G*Power. The program will then use these inputs to calculate and output the exact sample size required to achieve that desired level of statistical power.

Key points:

  • Explains that Dr. Aris inputs the expected relationship strength and α\alpha level.
  • Identifies the standard target power level to input as .80.80.
  • Explains that the tool uses these inputs to calculate the required sample size.

Rubric: The response must explain that Dr. Aris inputs the expected relationship strength, the α\alpha level, and the standard desired power of .80.80, and that G*Power uses these inputs to calculate the necessary sample size.

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Updated 2026-05-26

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Research Methods in Psychology - 4th American Edition @ KPU

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