Question: The TUF Telephone Company claims that on Mother’s Day the average phone call lasts longer than 31.25 minutes. A sample of 20 phone calls on Mother’s Day this year had a mean of 30.75 minutes and a sample standard deviation of 1.20 minutes. Using a level of significance of 1%, can you conclude that the mean length of phone calls on Mother’s Day isn’t greater than 31.25 minutes?