bConditional probability/b is when the probabililty of an event is dependent on the outcome of another event.

The probability that event (B) occurs given that event (A) has occurred is written is (P(B|A)).

(P(B|A) = \dfrac{P(B∩A)}{P(A)})

Alternatively:

(P(B|A)×P(A) = P(B∩A) )

For independent events:

(P(B|A) = P(B|A') = P(B) )

[b]uConditional probability[/u]/b

(P(B|A) = \dfrac{P(B∩A)}{P(A)})