Mốt của mẫu số liệu là: 

A. $\sqrt{S_X^2}$

B. $S_X^2$

C. $S_X^4$

D. $\sqrt{S_X}$ 

A. $S_X^2=\frac{1}{n}\left[n_1{\left(x_1-\overline{x}\right)}^2+n_2{\left(x_2-\overline{x}\right)}^2+\mathrm{...}+n_k{\left(x_k-\overline{x}\right)}^2\right]$

B. $S_X^2=\frac{1}{n}\left[{\left(x_1-\overline{x}\right)}^2+{\left(x_2-\overline{x}\right)}^2+\mathrm{...}+{\left(x_k-\overline{x}\right)}^2\right]$

C. $S_X^2={\left(x_1-\overline{x}\right)}^2+{\left(x_2-\overline{x}\right)}^2+\mathrm{...}+{\left(x_k-\overline{x}\right)}^2$

D. $S_X^2=\frac{1}{n^2}\left[n_1{\left(x_1-\overline{x}\right)}^2+n_2{\left(x_2-\overline{x}\right)}^2+\mathrm{...}+n_k{\left(x_k-\overline{x}\right)}^2\right]$ 

A. $\overline{x}=\frac{n_1{x}_1+n_2{x}_2+\mathrm{...}+n_k{x}_k}{n^2}$

B. $\overline{x}=\frac{n_1{x}_1+n_2{x}_2+\mathrm{...}+n_k{x}_k}{n}$

C. $\overline{x}=n_1{x}_1+n_2{x}_2+\mathrm{...}+n_k{x}_k$

D. $\overline{x}=n\left(n_1{x}_1+n_2{x}_2+\mathrm{...}+n_k{x}_k\right)$ 

A. $S_X^2=\frac{1}{n^2}\left[n_1{\left(x_1-\overline{x}\right)}^2+n_2{\left(x_2-\overline{x}\right)}^2+\mathrm{...}+n_k{\left(x_k-\overline{x}\right)}^2\right]$

B. $S_X=\frac{1}{n}\left[n_1{\left(x_1-\overline{x}\right)}^2+n_2{\left(x_2-\overline{x}\right)}^2+\mathrm{...}+n_k{\left(x_k-\overline{x}\right)}^2\right]$

C. $S_X=\sqrt{\frac{1}{n}\left[n_1{\left(x_1-\overline{x}\right)}^2+n_2{\left(x_2-\overline{x}\right)}^2+\mathrm{...}+n_k{\left(x_k-\overline{x}\right)}^2\right]}$

D. $S_X^2=\frac{1}{n}\sqrt{n_1{\left(x_1-\overline{x}\right)}^2+n_2{\left(x_2-\overline{x}\right)}^2+\mathrm{...}+n_k{\left(x_k-\overline{x}\right)}^2}$