A group of doctors published an article in the New England Journal of Medicine. In the article they revealed the findings of a study to determine if there is a difference in survival rates for men who undergo surgery for localized prostate cancer and those who are treated with observation only. The researchers randomly assigned 731 men with localized prostate cancer to radical prostaectomy(surgery) or observation. During the years of follow up, 245 of 367 assigned to surgery survived for at least 5 years and 223 of 364 men assigned to observation survived at least 5 years.

a) Construct and interpret 1 99% confidence interval for the difference in the true proportion of men like these that would survive for at least 5 years after receiving surgery and the proportion that would survive at least 5 years when only being observed.

b) Does the confidence interval provide convincing evidence that the true proportions differ? Justify your answer.