Question

袋中有4个黑球4个白球,不放回地随机取球直至有3个白球为止 求取出总球数的概率分布

Answer 1

分析：X是取出球总数,分布列如下P(X=3)=C(4,3)/C(8,3)=1/14P(X=4)=C(4,3)C(4,1)/C(8,4)=8/35P(X=5)=C(4,3)C(4,2)/C(8.5)=3/7P(X=6)=C(4,3)C(4,3)/C(8,6)=4/7P(X=7)=C(4,3)C(4,4)/C(8,7)=1/2