CFA Practice Question

There are 410 practice questions for this study session.

CFA Practice Question

A student's grade in a course is determined by her score on two exams. The probability that she passes the first exam is 0.85, the probability that she passes the second exam is 0.80, and the probability that she passes both exams is 0.78. What is the probability that she passes at least one of the exams?
A. 0.05
B. 0.83
C. 0.87
Explanation: Let A denote the event that she passes the first exam and B denote the event that she passes the second exam. P(A or B) = P(A) + P(B) - P(A and B) = 0.85 + 0.80 - 0.78 = 0.87

User Contributed Comments 2

User Comment
1a2a This is only true if the two events are independent, which is never specified in the problem?
myexam No, @1a2a: it does not matter if they are independent or not. If they are, P(A and B) = 0. In fact, because P(A and B) = 0.78 they are not independent.
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