15件产品中,有3件优质品,从这15件产品中随机的取出4件,求这4件产品中优质品件数的概率分布.

记这4件产品中优质品的件数为X
X可取0,1,2,3
P{X=0}=C(3,0)*C(12,4)/C(15,4)=495/1365=33/91
P{X=1}=C(3,1)*C(12,3)/C(15,4)=3*220/1365=44/91
P{X=2}=C(3,2)*C(12,2)/C(15,4)=3*66/1365=66/455
P{X=3}=C(3,3)*C(12,1)/C(15,4)=12/1365=4/455
分布列:
X 0,1,2,3
P 33/91,44/91 ,66/455,4/455