设x1,x2,···,xn是一组样本观测值,x是样本均值,则样本标准差是-|||-(A) sqrt (dfrac {1)(n)sum _(i=1)^n(({x)_(i)-overline (x))}^2} (B) sqrt (dfrac {1)(n-1)sum _(i=1)^n(({x)_(i)-overline (x))}^2}-|||-(C) dfrac (1)(n)sum _(i=1)^n(({x)_(i)-overline (x))}^2 (D) dfrac (1)(n-1)sqrt (sum _{i=1)^n(({x)_(i)-overline (x))}^2}

4.设x1,x2,···,xn是一组样本观测值,则其标准差是 () .-|||-A、 dfrac (1)(n-1)sqrt (sum _{i=1)^n(({x)

5.设x1,x2,···,xn是来自总体 sim N(mu ,(sigma )^2) 的样本,x为样本-|||-均值,令 =dfrac (sum _{i=1)^

1.设X1,X2,···,xn来自总体X的样本, (X)=(sigma )^2, overline (X)=dfrac (1)(n)sum _(i=1)^n(X

设X1,X2,···,Xn是正态总体N(μ,σ^2 )的样本,则 dfrac (1)(n)sum _(i=1)^n(({X)_(i)-overline (X))

5.11 设(X1,X2,···Xn, _(n)+1) 是正态总体N(μ,σ^2)的样本, overline (X)=-|||-dfrac (1)(n)sum

10.设x1,x2,···,xn为一个样本, ^2=dfrac (1)(n-1)sum _(i=1)^n(({x)_(i)-overline (x))}^2 是

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) ,

1.设总体 sim N(M,(sigma )^2) ,μ未知而σ^2已知,X1,X2,···,Xn是X的样本, overline (X)=dfrac (1)(n

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

(16)设X1,X2,···,xn为来自标准正态总体X的简单随机样本,记 overline (X)=dfrac (1)(n)sum _(i=1)^n(X)_(i