tex: detail stat analysis complexity

latex/content.tex

@@ -241,8 +241,10 @@ $ f_{U_{k-1}}(y) = 1 $.
 
 \section{Complexity and implementation optimization}
 
-The NFBP algorithm has a linear complexity $ O(n) $, as we only need to iterate
-over the items once.
+Both the NFBP and NFDBP algorithms have a linear complexity $ O(n) $, as we
+only need to iterate over the items once. While the algorithms themselves are
+linear, calculating the statistics may not not be. In this section, we will
+discuss how to optimize the implementation of the statistical analysis.
 
 \subsection{Performance optimization}