Conditional Probability

P(A|B) = probability of A given B has occurred = P(A∩B)/P(B), where P(B)>0. Reduces sample space to events consistent with B. Example: P(even number | >2) on a die: favorable = {4,6}, total from >2 is {3,4,5,6}, so P = 2/4 = 1/2.