Suppose we toss one fair, six-sided die. The sample space S = {1, 2, 3, 4, 5, 6}. Let A = face is 2 or 3 and B = face is even (2, 4, 6). To calculate P(A|B), we count the number of outcomes 2 or 3 in the sample space B = {2, 4, 6}. Then we divide that by the number of outcomes B (rather than S).

The number of outcomes that are 2 or 3 and also even

P(A/B) = P( A AND B) = _________________________6___________________________________ =

P(B) all even numbers on the die

6