A class survey in a large class for first-year college students asked, "About how many hours do you study during a typical week?" The mean response of a random sample of 484 students was 13.7 hours. Suppose that we know that the study time follows a Normal distribution with standard deviation = 11 hours in the population of all first-year students at this university.

a) Give a 98% confidence interval for the mean study time of all first-year students.

There were actually 485 responses to the class survey. One student claimed to study 10,000 hours per week. We know he's joking, so we left out this value. If we did a calculation without looking at the data, we would get the sample mean of 35.2 hours for all 485 students.

b) What is the 98% confidence interval for the population mean? Continue to use = 11.