55单选题设 _(xy)=sum _(xarrow {y)_(4)}((x)_(i)-overline (x))((y)_(i)-overline (y)) , _(xx)=sum _(i=1)^n(({x)_(i)-overline (x))}^2 , _(w)=sum _(i=1)^7(({y)_(i)-overline (y))}^2-|||-则样本相关系数与回归系数的数量关系是()。-|||-overline ({B)_(1)}=rsqrt (dfrac {{L)_(x)x}({L)_(yy)}}-|||-=(hat {B)}_(1)sqrt (dfrac {{L)_(yy)}({L)_(xx)}}-|||-overline ({B)_(1)}=rsqrt (dfrac {{L)_(y)y}({L)_(x)x}}-|||-D =sqrt (1-{{P)_(1)}^2}

设_(xy)=sum _(i=1)^4((x)_(i)-overline (x))((y)_(i)-overline (y))，_(xy)=sum _(i=1)

(B) dfrac (1)(n+1)sum _(i=1)^n(({X)_(i)-overline (X))}^2 .-|||-(C) dfrac (1)(n)s

设X_1, X_2, ldots, X_n是来自总体N(mu, sigma^2)的样本，令Y = (sum_(i=1)^n(X_i - overline(X))

.-(x)^2(n) 的简单随机样本, overline (X)=dfrac (1)(n)sum _(i=1)^n(X)_(i) ,则-|||-|E(overl

令 Y = (1)/(n) sum_(i=1)^n X_i，则A. $\Cov(X_1, Y)= \frac{\sigma^2}{n}$.B. $Cov(X_1

dfrac (1)(n-1)sum _(i=1)^n(({X)_(i)-overline (X))}^2 .-|||-n-|||-C. sqrt (dfrac

单选题 已知 X_(1),X_(2),L,X_(50) 为来自总体 X:N(2,4) 的样本，记 overline(X)=(1)/(50)sum_(i=1)^5

3.设X_(1),...,X_(10)为来自标准正态总体Xsim N(0,1)，Y_(1)=7sum_(i=1)^3X_(i)^2,Y_(2)=3sum_(i=

=2-|||-4.设X1,X2,···,x3是来自总体 approx N(1,4) 的简单随机样本, overline (X)=dfrac (1)(n)sum

(B) (hat {sigma )}^2=dfrac (1)(n)sum _(i=1)^n(({X)_(i)-overline (X))}^2.-|||-(C