概奉论与散理统计「 A={1,2),(1,3),(1,4)(2,1),(2,3),(2,4), (3,1),(3,2),(3,4), AB={1,2),(1,3),(2,1),(2,3),(3,1),(3,2)}, 由条件概率的公式得 P(BA)= P(AB) P(A) 6/122 9/12-3(3,1), (3,2), (3,4)}, A {(1,2), (1,3), (1,4), (2,1), (2,3), (2,4), AB {(1,2), (1,3), (2,1), (2,3), (3,1), (3,2)}, 由条件概率的公式得 ( ) ( ) ( ) P A P AB P B A 9 12 6 12 . 3 2