Multiplication Rule of Probability: with Examples
The general formula for the probability of two events, A and B, happening at the same time (or the "joint probability" of A and B) is given by one or the other of the following formulae, where
P(B | A) is the probability of the event B conditional on the occurrence of A and
P(A | B) is the probability of the event A conditional on the occurrence of B.
P(A and B) = P(A) · P(B | A)
P(A and B) = P(B) · P(A | B).
If the events A and B are independent (that is, the occurrence of one does not affect the occurrence of the other), the Multiplication Rule is simplied to the following:
P(A and B) = P(A) ยท P(B) since P(B | A) = P(B).
Last Updated by SAS October 07, 2026, 16:00:54
