- 期望与方差随机变量X的分布函数F(x)=0(x<
- 随机变量X的分布
F(x)=
0(x<-1)
0.4(-1≤x<1
0.8(1≤x<3)
1(x≥3)
求(1)X的分布律
(2)X的期望EX
(3)X的方差DX
- (1)
P(X=-1)=0.4
P(X=1)=0.8-0.4=0.4
P(X=3)=1-0.8=0.2
(2)
EX=(-1)*0.4+1*0.4+3*0.2=0.6
(3)
EX^2=(-1)^2*0.4+1^2*0.4+3^2*0.2=2.6
DX=EX^2-(EX)^2=2.6-0.36=2.24