, F ≠ φ (Why )
Thus, we can define the conditional probability as follows :
Definition 1 If  E and F are two events associated with the same sample space of a
random experiment, the conditional probability of the event E given that F has occurred,
i e P (E|F) is given by
P(E|F) = P(E
F)
P(F)
∩
 provided P(F) ≠ 0
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