In a study of computer use, 1000 randomly selected Canadian Internet users were asked how much time they spend using the Internet in a typical week (1psos Reid, August 9, 2005). The mean of the sample observations was 12.7 hours.
a. The sample standard deviation was not reported, but suppose that it was = hours. Carry out a hypothesis test with a significance level of .05 to decide if there is convincing evidence that the mean time spent using the Internet by Canadians is greater than 12.5 hours.
b. Now suppose that the sample standard deviation was 2 hours. Carry out a hypothesis test with a significance level of .05 to decide if there is convincing evidence that the mean time spent using the Internet by Canadians is greater than 12.5 hours.
c. Explain why the null hypothesis was rejected in the test of Part (b) but not in the test of Part (a).