Question

Answer questions 3 and 4 based on the following. A survey of business students who had taken the Graduate Management Admissions Test (GMAT) indicated that students who have spent at least five hours studying GMAT review guides have a probability of 0.85 of scoring above 400. Students who do not review in this way have a probability of 0.65 of scoring above 400. It has been determined that 70% of the business students review for the test.

3. Compute the probability of scoring above 400. a. 0.12 b. 0.20 c. 0.55 d. 0.79 e. 1.50

4. Given that a student scored above 400, what is the probability that he/she reviewed for the test? a. 0.15 b. 0.27 c. 0.60 d. 0.75 e. 0.85

Answer 1

Answer )

(a)

Probability of them scoring above 400 = (probability they review for the test and probability they get above 400 while doing so) +( probability they don't review for the test and scoring above 400)

= 0.85*0.7 + 0.65 *0.3 = 0.79

Hence, correct option is (d) 0.79.

(b) To help conceptualize this question, assume there are 100 students. 70 of them study, and 30 of them don't. Out of the 70 that study, 85% of them get above 400, which is 59.5 students. 65% of the 30 students also passed, or 19.5 students.

So,the probability that a student who scored 400 reviewed for the test = 59.5/79 = 0.7531 0.75

So, correction option is (d) 0.75.