, En has nonzero probability of occurrence Let A be any event associated
with S, then
P(A) = P(E1) P(A|E1) + P(E2) P(A|E2) + + P(En) P(A|En)
=
1
P(E )P(A|E )
n
j
j
j=∑
Proof  Given that E1, E2, , En is a partition of the sample space S (Fig 13