5、判断设总体 approx N((H)_(2)(O)^2), X1,X2,···,Xn是从总体UND中-|||-抽取的样本,记 overline (X)=dfrac (1)(n)sum _(i=1)^n(X)_(i), ^2=dfrac (1)(n-1)sum _(i=1)^n(({x)_(i)-overline (x))}^2, 则S^2既是σ^2的矩估计-|||-也是σ^2的最大似然估计。-|||-5分)-|||-A x-|||-B