High levels of cholesterol in the blood are associated with higher risk of heart attacks. Will using a drug to lower blood cholesterol reduce heart attacks? The Helsinki Heart Study looked at this question. Middle-aged men were assigned at random to one of two treatments: 2051 men took the drug gemfibrozil to reduce their blood cholesterol levels, and a control group of 2030 men took a placebo. During the next five years, 65 men in the gemfibrozil group and 84 men in the placebo group had heart attacks. Is there a significant difference between the heart attack rate of those who took gemfibrozil and the rate of those who received the placebo?
a. Calculate the value of the two tail z test for two proportions. Round your answer to 2 decimal points.
b. Find the lower bound of 99% CI for the difference in two proportions.
c. Calculate the upper bound of 99% CI for the difference of the two proportions.
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