We wish to design a study to assess risk factors for stroke and dementia. There are two primary outcome measures. The first is a measure of neurological function. Patients with normal function typically score 70 with a standard deviation of 20. The second outcome is incident stroke. In patients over the age of 65, approximately 15% develop stroke over 25 years. a. That the margin of error in a 95% confidence interval for the difference in mean neurologic function scores between men and women does not exceed 3 units. b. That we have 90% power to detect a 20% reduction in incidence of stroke between participants who participate in a healthy aging program as compared to those who do not. Assume that the incidence of stroke is 15% in those who do not participate and 20% lower in the group who participate.