CMA Foundation · Fundamentals of Business Mathematics and Statistics · Probability
For two events A and B, P(A) = 0.5, P(B) = 0.4 and P(A and B) = 0.2. What is P(A given B)?
P(A given B) equals 0.5. Conditional probability is the joint probability divided by the probability of the given event, so 0.2 divided by P(B) = 0.4 gives 0.5. Dividing by P(A) would wrongly give P(B given A) = 0.4.
- A0.4
- B0.5Correct
- C0.2
- D0.8
Explanation
P(A|B) = P(A and B)/P(B) = 0.2/0.4 = 0.5. The value 0.4 comes from dividing by P(A) instead, which gives P(B|A).
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