试题题干
参考答案
试题解析
方差公式：D(X)=E(X²)-[E(X)]²
E(X)=-1×0.1+0×0.2+1×0.3+2×0.4=1
X²的取值有：0、1、4
P{X²=0}=0.2、P{X²=1}=0.1+0.3=0.4、P{X²=4}=0.4
E(X²)=0×0.2+1×0.4+4×0.4=2
D(X)=E(X²)-[E(X)]²=1
方差公式：D(X)=E(X²)-[E(X)]²
E(X)=-1×0.1+0×0.2+1×0.3+2×0.4=1
X²的取值有：0、1、4
P{X²=0}=0.2、P{X²=1}=0.1+0.3=0.4、P{X²=4}=0.4
E(X²)=0×0.2+1×0.4+4×0.4=2
D(X)=E(X²)-[E(X)]²=1