more typos

doc/BookChapters/chapter2.do.txt

@@ -1288,7 +1288,7 @@ For the sake of simplicity, let us assume that the design matrix is orthonormal,
 In this case the standard OLS results in 
 !bt
 \[
-\bm{\beta}^{\mathrm{OLS}} = \bm{X}^T\bm{y}=\sum_{i=0}^{p-1}\bm{u}_j\bm{u}_j^T\bm{y},
+\bm{\beta}^{\mathrm{OLS}} = \bm{X}^T\bm{y}=\sum_{i=0}^{n-1}\bm{u}_i\bm{u}_i^T\bm{y},
 \]
 !et