According to the National Survey of Student Engagement, the average student spends about 15 hours each week preparing for classes; preparation for classes includes homework, reading and any other assignments.

a. what is the probability that the mean time spent preparing for classes is at least 14 hours per week.

b. There is an 85% chance that the sample mean is less than how many hours per week?

c. What assumption must you make in order to solve (a) and (b)?

d. If you select a random sample of 64 students there is an 85% chance that the sample mean is leaa than how many hours per week?