7.设X_(1),X_(2),X_(3)是来自总体Xsim N(0,1)的一组样本，则X_(1)+X_(2)+X_(3)：____，X_(1)^2+X_(2)^
3.(填空题)3.设X_(1),...,X_(5)是来自总体X的样本，且Xsim N(0,1)，则k=____时，kcdot(X_(1)^2+X_(2)^2+X
设(X_(1),X_(2),X_(3),X_(4))是总体X的简单随机样本，X~N(0,4)，F=C(X_(1)^2)/(X_(2)^2+X_{3)^2+X_(
1 设总体Xsim N(0,1)，X_(1),X_(2),...,X_(n)为X的样本，则((X_(1)-X_(2))/(X_(3)+X_{4)})^2服从__
设X_(1),X_(2),...,X_(n)为总体Xsim N(mu,sigma^2)的样本，证明hat(mu)_(1)=(1)/(2)X_(1)+(2)/(3
4.(1)设样本X_(1),X_(2),...,X_(6)来自总体N(0,1),Y=(X_(1)+X_(2)+X_(3))^2+(X_(4)+X_(5)+X_(
16.设总体Xsim N(0,1)，X_(1),X_(2),X_(3),X_(4)是来自总体X的简单随机样本，又设Y=(X_(1)+X_(2))^2+(X_(3
1.设随机变量X_(1),X_(2),X_(3),X_(4)相互独立，服从相同的正态分布N(mu,sigma^2)，则Y=(1)/(2sigma)(X_(1)^
X_(n)是取自总体N(0,1)的样本，则X^2=X_(1)^2+X_(2)^2+X_(3)^2simchi^2(_).5.设$X_{1},X_{2},\cdo
X_(4))为来自总体X的简单随机样本，则k=（ ）时，Y=k[(X_(1)-X_(2))^2+(X_(3)-X_(4))^2]sim X^2(2).A. 16