Given, A and B are two events of a sample space S such that P(A) = 0.2, P(B) = 0.6 and P(A|B) = 0.5 To find: P(A'|B) By complementary rule of Conditional probability, P(A'|B) = 1 - P(A|B) ⇒P(A'|B) = 1 - 0.5 ⇒P(A'|B) = 0.5 Hence, If A and B are two events of a sample space S such that P(A) = 0.2, P(B) = 0.6 and P(A|B) = 0.5 P(A'|B) = 0.5