As the end of the semester approaches, you wonder whether there is a relationship betweenthe number of exams a student has during the last week of class and the amount of sleep a student gets during that week. You collect a sample of 15 undergraduates and ask them to report the number of tests they had scheduled as well as the number of hours they slept during the final week of classes last semester.

8. For your sample, you find that SSx (number exams) = 25.6, SSy (hours sleep) = 1660, and the

sum of products = -170. Calculate the Pearson correlation coefficient. (4)