A survey in a large unit for first-year college students asked, "About how many hours do you exercise during a week?" The mean response of the 606 students was = 2.1 hours. Suppose that we know that the standard deviation of exercise time is = 1.4 hours in the population of all first-year students at this college.

a) Find the point estimate of the mean time in exercising for a week in the population of all first- year students at this college.

b) Check conditions for a confidence interval for the mean exercise time of all first-year students.

c) Use the survey result to give a 95% confidence interval for the mean exercise time of all first-

year students. Interpret the confidence interval.

d) Give a 99% confidence interval for the mean exercise time of all first-year students.

e) Compare the confidence intervals in c) and d).