Refer to Exercise 22. Of the 193 placebo takers, 43 reported headaches.
a. Compute a 95% confidence interval for the true population proportion that would get headaches after taking a placebo.
b. Notice that a higher proportion of placebo takers than Seldane-D takers reported head­aches. Use that information to explain why it is important to have a group taking placebos when studying the potential side effects of medications.