Question: Your research group is investigating the efficacy of an intervention designed to prevent cognitive decline among older adults. A group of subjects will be assigned to receive a daily structured cognitive training exercise, while the other group will receive no intervention. Based on previous research, you expect that 15% of those in the control arm will meet the criteria for Mild Cognitive Impairment (MCI) after one year. You are hoping that the cognitive training intervention will reduce this risk to 5%.

1. Assuming equal group sizes and a type I error rate of 5%, how many participants would you need in your study to achieve 80% power?
2. Suppose you are not able to recruit as many subjects as you calculated in a). Holding all else constant, how would this affect the power of your study?
3. Suppose you decided that even a 10% risk of MCI in the intervention group (compared to the expected 15% risk in the control group) would be a clinically meaningful reduction of risk. Holding all else constant, how would the sample size needed to achieve 80% power in this scenario compare to the sample size calculated in a)?

Price: $2.99

Solution: The downloadable solution consists of 2 pages
Deliverable: Word Document