5.28 - Total Sleep Time of College Students In example, 5.4, the total sleep time per night among college students was approximately normally distributed with a mean = 6.78 hours and standard...

5.28 - Total Sleep Time of College Students

In example, 5.4, the total sleep time per night among college students was approximately normally distributed with a mean = 6.78 hours and standard deviation = 1.24 hours. You plan to take an SRS of size n=120 and compute the average total sleep time.

a. What is the standard deviation for the average time?

b. Use the 95 part of the 68-95-99.7 rule to describe the variability of this sample mean.

c. What is the probability that your average will be below 6.9 hours?