Suppose that 60 internet-users are randomly selected and monitored to see how long

each user spends on Facebook daily. The average amount of time spent on Facebook

among these users turned out to be 40 minutes per day with a standard deviation of 15

minutes.

(a) Find a Confidence interval for the average amount of time spent on Facebook by

all internet-users which has a confidence level of 99%.

(b) What does the confidence interval in (a) tell us?