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.
Assume the standard deviation of time spent preparing for classes is 4 hours. If you select a random sample of 16 students,
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 less than how many hours per week?