In a Random Sample of 12 Calls Made from the U.S.to

Multiple Choice

In a random sample of 12 calls made from the U.S.to Japan by callers using Skype during the past week, the average call lasted 21.4 minutes, with a sample standard deviation of 5.1 minutes.Assume the population distribution of call times is normal.Build a 99% confidence interval estimate of the average call time for the population of calls represented by the sample (that is, the population of all calls made from the US to Japan last week by callers using Skype) .Report the upper bound for your interval.

A) 28.92
B) 24.01
C) 25.98
D) 22.36
E) 26.89