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(Probability given something happened)
The conditional probability P(A | B) reads "probability of A given B". It is the probability A happens, knowing B already happened.
Formula: P(A | B) = P(A ∩ B) / P(B), when P(B) > 0.
If you know it rained, what is the chance you brought an umbrella? That is P(umbrella | rain).
