- CFA Exams
- CFA Level I Exam
- Study Session 2. Quantitative Methods (1)
- Reading 8. Probability Concepts
- Subject 3. Addition Rule for Probabilities: the Probability that at Least One of Two Events Will Occur
CFA Practice Question
The manager of a pension fund determines that during the past five years 85 percent of the stocks in the portfolio have paid a dividend and 40 percent of the stocks have announced a stock split. If 95 percent of the stocks have paid a dividend and/or announced a stock split, the joint probability of a stock paying a dividend and announcing a stock split is closest to ______.
A. 25%
B. 30%
C. 40%
Explanation: The probability that at least one of two events will occur is the sum of the probabilities of the separate events less the joint probability of the two events.
95% = 85% + 40% - P(AB); therefore P(AB) = 30%
P(A or B) = P(A) + P(B) - P(AB)
95% = 85% + 40% - P(AB); therefore P(AB) = 30%
User Contributed Comments 2
User | Comment |
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aleakos | Is this right? It says the probability that a stock has paid a dividend AND/OR paid a stock is 95 percent. Doesn't this mean that the p(a or b)+ p(ab)=95%, or am I being dumb? |
aleakos | Nevermind I'm being dumb, or is inclusive |