Today, full- time college students report spending a mean of 27 hours per week on academic activities, both inside and outside the classroom. (Source: “ A Challenge to College Students for 2013: Don’t Waste Your 6,570,” Huffington Post, January 29, 2013, huff. to/ 13dNtuT.) Assume the standard deviation of time spent on academic activities is 4 hours. If you select a random sample of 16 full- time college students,

a. What is the probability that the mean time spent on academic activities is at least 26 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 full- time college students, there is an 85% chance that the sample mean is less than how many hours per week?