Apply the sample size benchmarks for an independent-samples -test with a large population effect to Dr. Aris's study. Determine how many participants she must recruit per group to achieve a power of , how many she would need to achieve a power of , and justify whether she should adjust her initial plan of participants per group.
Case context: Dr. Aris is designing an experimental study comparing a new mindfulness technique to an active control group using an independent-samples -test. Based on past literature, she expects a large population effect size. She initially plans to recruit participants per group, but a senior colleague advises her that this sample size might be insufficient to achieve acceptable statistical power.
Question: Apply the sample size benchmarks for an independent-samples -test with a large population effect to Dr. Aris's study. Determine how many participants she must recruit per group to achieve a power of , how many she would need to achieve a power of , and justify whether she should adjust her initial plan of participants per group.
Sample answer: Dr. Aris must adjust her initial plan of participants per group because it is insufficient to achieve the standard statistical power of . For an independent-samples -test with a large population effect, she needs approximately participants per sample to reach a power of . If she wishes to achieve a very high statistical power of , she would need to recruit participants per sample. Therefore, she should increase her sample size to at least participants per group, or up to per group if she wants to ensure an extremely low probability of a Type II error.
Key points:
- Identifies that Dr. Aris's initial plan of participants per group is insufficient to reach the standard power of .
- Applies the benchmark of approximately participants per sample to achieve a power of .
- Applies the benchmark of approximately participants per sample to achieve a power of .
- Justifies the recruitment adjustment by linking sample sizes to the desired power levels and control of statistical error.
Rubric: The student must apply the sample size benchmarks of (for power) and (for power) to Dr. Aris's case. They must correctly identify that her current plan of is too small to reach even power, and recommend adjusting the recruitment targets upward to either or participants per group with appropriate statistical justification.
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Research Methods in Psychology - 4th American Edition @ KPU
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Apply the sample size benchmarks for an independent-samples -test with a large population effect to Dr. Aris's study. Determine how many participants she must recruit per group to achieve a power of , how many she would need to achieve a power of , and justify whether she should adjust her initial plan of participants per group.
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