差分

:Variance <math>= \frac{\sum_{i=1}^n (x_i - \bar x)^2}{n-1}</math> | :Sum of square <math>= {\sum_{i=1}^n (x_i - \bar x)^2}</math> Here we think a case to divide the observations into <math>k</math> groups.:<math>x_1, x_2, \cdots ,x_n</math>:→<math>\begin{Bmatrix}x_1, x_2, \cdots \\\vdots & \ddots &\vdots \\\cdots x_{n-1}, x_n\end{Bmatrix}</math>  , the sum of square of the total observations can be transformed as follows: :<math>\begin{align}{\sum_{i=1}^n (x_i - \bar x)^2} & = \\ \end{align}</math>