设_(xy)=sum _(i=1)^4((x)_(i)-overline (x))((y)_(i)-overline (y))，_(xy)=sum _(i=1)^4((x)_(i)-overline (x))((y)_(i)-overline (y))，则样本相关系数与回归系数的数量关系是（ ）。A._(xy)=sum _(i=1)^4((x)_(i)-overline (x))((y)_(i)-overline (y))B._(xy)=sum _(i=1)^4((x)_(i)-overline (x))((y)_(i)-overline (y))C._(xy)=sum _(i=1)^4((x)_(i)-overline (x))((y)_(i)-overline (y))D._(xy)=sum _(i=1)^4((x)_(i)-overline (x))((y)_(i)-overline (y))

55单选题设 _(xy)=sum _(xarrow {y)_(4)}((x)_(i)-overline (x))((y)_(i)-overline (y)) ,

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

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

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

=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

4.样本X1,X2,···Xn来自总体 sim N(0,1) , overline (X)=dfrac (1)(n)sum _(i=1)^n(X)_(i) ,

4.设总体 sim N(mu ,(sigma )^2), x1,x2,···,xn为样本,证明 overline (x)=dfrac (1)(n)sum _(i

设总体 X sim N(0,1)，(X_1,X_2,...,X_n) 是总体 X 的样本，令 overline(X)=(1)/(n)sum_(i=1)^nX_i

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))