A.0.2               B.0.196               C.0.8                 D.0.812

某牧场的10头牛因误食疯牛病毒污染的饲料被感染,已知疯牛病发病的概率为0.02.若发病的牛数为ξ,则Dξ等于

A.0.2                   B.0.196                   C.0.8                     D.0.812

A.0.2               B.0.196               C.0.8                 D.0.812

某牧场的10头牛因误食疯牛病毒污染的饲料被感染,已知疯牛病发病的概率为0.02.若发病的牛数为ξ,则Dξ等于

1. A.
   0.2
2. B.
   0.196
3. C.
   0.8
4. D.
   0.812