The researchers also need to obtain precise estimates of the mean difference in systolic blood pressures for people who use the anti-inflammatory drug versus those who do not.
a. Suppose the sample sizes are the same for both groups. What sample size is needed to obtain a 95% confidence interval for the mean difference in systolic blood pressure between the users and nonusers having a width of at most 5 mm Hg.
b. Suppose the user group will have twice as many patients as the placebo group. What sample size is needed to obtain a 95% confidence interval for the mean difference in systolic blood pressures between the users and nonusers having a width of at most 5 mm Hg.