1.总体X的均值μ与方差σ^2的矩估计为 () .-|||-A.X, dfrac (1)(n)sum _(i=1)^n(({x)_(i)-overline (X))}^2 B.X dfrac (1)(n-1)sum _(i=1)^n(({x)_(i)-overline (X))}^2-|||-C.X,X^2 D.X, dfrac (x)(2)