4. Average annual expenditures on health care for young people are considerably lower than those for the 75 years and older age group. Suppose we draw a random sample of 954 consumer units for the under-25 years age group, and calculate a mean (X ) of $682 and a sample standard deviation (s) of $5,350. . (a) Explain which one of the two probability distributions discussed in Chapter 10 is more appropriate to use for estimating the confidence intervals in parts (b) and (d) below. (b) Compute the 95 percent confidence interval for the population mean. (c) Fully interpret the results in part (b). (d) Demonstrate how the confidence interval changes for i. a 90 percent confidence level ii. a 99 percent confidence level. (e) Discuss what the differences in the results in parts (b) and (d) indicate about the statistical estimation of the population mean