设(X1,X2,……,Xn)是取自正态总体N(U,δ^2)的样本,

问题描述:

设(X1,X2,……,Xn)是取自正态总体N(U,δ^2)的样本,
则EX(X上面一横杠)=( ),DX(X上面一横杠)=( )

EX(X上面一横杠)=E[(X1+X2+……+Xn)/n]
=1/n [E(X1)+E(X2)+……+E(Xn)]
=1/n (U+U+……+U)
=U
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