From: Wu Zhang <wuzhang50@ya...>  20131005 21:22:00

Hi, I found this file for probability tree: \documentclass{article} \usepackage[latin1]{inputenc} \usepackage{tikz} \usetikzlibrary{trees} \usepackage{verbatim} \begin{comment} :Title: Probability tree :Tags: Trees A simple example of a probability tree diagram. \end{comment} \begin{document} \pagestyle{empty} % Set the overall layout of the tree \tikzstyle{level 1}=[level distance=3.5cm, sibling distance=3.5cm] \tikzstyle{level 2}=[level distance=3.5cm, sibling distance=2cm] % Define styles for bags and leafs \tikzstyle{bag} = [text width=4em, text centered] \tikzstyle{end} = [circle, minimum width=3pt,fill, inner sep=0pt] % The sloped option gives rotated edge labels. Personally % I find sloped labels a bit difficult to read. Remove the sloped options % to get horizontal labels. \begin{tikzpicture}[grow=right, sloped] \node[bag] {Bag 1 $4W, 3B$} child { node[bag] {Bag 2 $4W, 5B$} child { node[end, label=right: {$P(W_1\cap W_2)=\frac{4}{7}\cdot\frac{4}{9}$}] {} edge from parent node[above] {$W$} node[below] {$\frac{4}{9}$} } child { node[end, label=right: {$P(W_1\cap B_2)=\frac{4}{7}\cdot\frac{5}{9}$}] {} edge from parent node[above] {$B$} node[below] {$\frac{5}{9}$} } edge from parent node[above] {$W$} node[below] {$\frac{4}{7}$} } child { node[bag] {Bag 2 $3W, 6B$} child { node[end, label=right: {$P(B_1\cap W_2)=\frac{3}{7}\cdot\frac{3}{9}$}] {} edge from parent node[above] {$B$} node[below] {$\frac{3}{9}$} } child { node[end, label=right: {$P(B_1\cap B_2)=\frac{3}{7}\cdot\frac{6}{9}$}] {} edge from parent node[above] {$W$} node[below] {$\frac{6}{9}$} } edge from parent node[above] {$B$} node[below] {$\frac{3}{7}$} }; \end{tikzpicture} \end{document} You can find the link here: https://www.writelatex.com/402223pmfdhy My question is: how can we replace the fractions with a box or circle? I am planning to put it as a question to students; I want them to fill out the box or circles for the right probabilities. Thanks, Wu 