. It is assumed that the mean systolic blood pressure in the population is 120 mm Hg. Suppose systolic blood pressure comes form a normal distribution. In a study, a sample of 10 people had an average systolic blood pressure of 131.2 mm Hg with a standard deviation of 25.55 mm Hg. (a) Is the mean systolic blood pressure significantly different from the assumption stated at the beginning of the problem? Find the appropriate confidence interval to answer this question. (b) What sample size is needed to estimate mean systolic blood pressure with 95% confidence within 7 mm Hg?