21.3 Blood pressure of executives. The medical director of a large company looks at the medical records of 72 executives between the ages of 35 and 44 years. He finds that the mean systolic blood pressure in this sample is and the standard deviation is s = 15.2. Assuming the sample is a random sample of all executives in the company, find a 95% confidence interval for μ, the unknown mean blood pressure of all executives in the company.