III.3. Grades in an economics course. Indiana University posts the grade distributions for its courses online. Students in Economics 201 in the fall 2013 semester received 18% A’s, 8% A−’s, 7% B+’s, 16% B’s, 11% B−’s, 6% C+’s, 12% C’s, 4% C−’s, 3% D+’s, 6% D’s, 4% D−’s, and 6% F’s. Choose an Economics 201 student at random. The probabilities for the student’s grade are:
| Grade | A | A− | B+ | B |
| Probability | 0.18 | 0.08 | 0.07 | 0.16 |
| Grade | B− | C+ | C | C− |
| Probability | 0.11 | 0.06 | 0.12 | 0.04 |
| Grade | D+ | D | D− | F |
| Probability | 0.03 | 0.06 | 0.04 | ? |
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(a) What must be the probability of getting an F? (Hint: See page 429.)
(b) To simulate the grades of randomly chosen students, how would you assign digits to represent the five possible outcomes listed? (Hint: See page 447.)