In a drug test for adverse reactions it was found that 734 men treated with Xanax, 16% experienced headaches. Among 725 men in the placebo group, 4% experienced headaches.

a) Using a 0.01 significance level, is there sufficient evidence to support the claim that among those men who take Xanax,headaches occur at a rate that is greater than the rate of those who do not take Xanax?

b) Construct a 99% Confidence interval estimate of the difference between the rate of headaches among Xanax users and the headache rate for those who use placebo. What does the confidence interval suggest about the two rates?