平方和の分解
$ S_T = S_R+S_e.
$ S_{T}=\sum_{k=1}^{n}\left(y_{k}-\overline{y}\right)^{2}: 総平方和 $ S_{R}=\sum_{k=1}^{n}\left(\widehat{y}_{k}-\overline{y}\right)^{2}: 回帰平方和 $ S_{e}=\sum_{k=1}^{n}\left(y_{k}-\widehat{y}_{k}\right)^{2}: 残差平方和 $ \phi_T=\phi_R+\phi_e.