orígen TeX:
{\displaystyle \sum_{i=1}^{k}\sum_{j=1}^{n_{i}}\left(y_{ij}-\bar{y}\right)^{2}=n\sum_{i=1}^{k}\left(\bar{y}_{i}-\bar{y}\right)^{2}+\sum_{i=1}^{k}\sum_{j=1}^{n_{i}}\left(y_{ij}-\bar{y}_{i}\right)^{2}}