As a university instructor who has been teaching statistics for a number of years, I have been asked by my School Director to report what the mean course grade was for students who enrolled in CRIMJ 260 this past academic year (sample 1, 80 students). Since you cannot ignore a question that comes from a School Director, I think about it in my office one afternoon while playing solitaire and downloading music on my computer. After a couple quick calculations, I call the School Director and say that that mean course grade was 70, standard deviation 10. He says, Well, Don, that is an awfully low mean. Why dont you take a sample of students who have taken your statistics classes over the previous 2 years, and see what mean score that sample received? (sample 2).

I hang up the phone and curse the School Director. Then I randomly select 100 students who have taken my statistics classes over the previous 2 years and find that the samples mean course grade was 72, with a standard deviation of 11. Calculate the t-statistic for comparing these two samples. It is ______.

A. 0

B. 1.266

C. 1.577

D. 2.488