Coronary bypass surgery: A healthcare research agency reported that 54% of people who had coronary bypass surgery in 2008 were over the age of 65. Twelve coronary bypass patients are sampled. (a) What is the mean number of people over the age of 65 in a sample of 12 coronary bypass patients? Round the answer to two decimal places. The mean number of people over the age of 65 is D. (b) What is the standard deviation of the number of people over the age of 65 in a sample of 12 coronary bypass patients? Round the answer to four decimal places. The standard deviation of the number of people over the age of 65 is [:l