We wish to design a study to compare two antihypertensive medications. Two outcome variables will be considered: systolic and diastolic blood pressure. a. How many subjects would be required to detect...

We wish to design a study to compare two antihypertensive medications. Two outcome variables will be considered: systolic and diastolic blood pressure.

a. How many subjects would be required to detect with 80% power and a = 0.05 a difference of 20 units in mean systolic blood pressures between groups? Assume that the standard deviation in systolic blood pressure is 25.

b. How many subjects would be required to detect with 80% power and a = 0.05 a difference of 10 units in mean diastolic blood pressures between groups? Assume that the standard deviation in diastolic blood pressure is 21.

c. What is the minimum number of subjects we need to satisfy both (a) and (b)?

d. Suppose that this study involves enrolling patients and measuring their blood pressures after 6 months--at which time the medications should show an effect. If 10% of the patients drop out of the study within 6 months, how many patients need to be enrolled to satisfy the requirements of (c)?