diff --git a/book/2-regression.tex b/book/2-regression.tex
index 757a898..93976ce 100644
--- a/book/2-regression.tex
+++ b/book/2-regression.tex
@@ -540,7 +540,7 @@ \subsection{Mean Poisson Deviance}
         \node[inner sep=2pt, font=\Large] (a) {
             {
                 $\displaystyle
-                MPD = \frac{1}{{\color{nmlred}n}} \sum_{t=1}^{n} 2 \left( {\color{nmlpurple}Y_i} \log ( \frac {\color{nmlpurple}Y_i}{\color{nmlcyan}\hat{Y}_i} ) - ( {\color{nmlpurple}Y_i} - {\color{nmlcyan}\hat{Y}_i} ) \right)
+                MPD = \frac{1}{{\color{nmlred}n}} \sum_{t=1}^{n} 2 \left( {\color{nmlpurple}Y_i} log ( \frac {\color{nmlpurple}Y_i}{\color{nmlcyan}\hat{Y}_i} ) - ( {\color{nmlpurple}Y_i} - {\color{nmlcyan}\hat{Y}_i} ) \right)
                 $
             }
         };