The College Board website provides much information for students, parents, and professionals with respect to the many aspects involved in Advanced Placement (AP) courses and exams. One particular annual report provides the percent of students who obtain each of the possible AP grades (1 through 5). The 2008 grade distribution for all subjects was as follows:
AP Grade Percent
1........ 20.9
2........ 21.3
3........ 24.1
4........ 19.4
5........ 14.3
a. Express this distribution as a discrete probability distribution.
b. Find the mean and standard deviation of the AP exam scores for 2008.