bloyfly4
幼苗
共回答了15个问题采纳率:86.7% 举报
X的均值
E(X)=(-50)*0.1+(-20)*0.2 +0*0.2 +30*0.3 + 50*0.2=-5-4+0+9+10=10
X^2的均值
E(X^2)=(-50)^2*0.1+(-20)^2*0.2+0^2*0.2+30^2*0.3+50^2*0.2=250+80+0+270+500=1100
X的方差
D(X)=E[X-E(X)]^2=E(X^2)-[E(X)]^2=1100-10^2=1000
X的标准方差 为31.62
1年前
6