\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{arrows,shapes,chains}
\begin{figure}
\tikzstyle{startstop} = [rectangle, text centered, draw = black, fill = white]
\tikzstyle{arrow} = [->,>=stealth]
\begin{tikzpicture}
\node(assum)[startstop] {Assumption};
\node(fprop)[startstop,below of=assum,yshift=-0.2cm, left of = assum, xshift=-1cm]{Formal Proportion};
\node(eprop)[startstop,right of = fprop, xshift = 4cm]{Empirical Proposition};
\node(test)[startstop, blow of = eprop, yshift = -0.2cm]{Test by Data};
\node(theory)[startstop, blow of = test, yshift = -0.2cm,left of = test, xshift = -1cm]{Wrong Theory};
\node(assump)[startstop, blow of = test, right of = theory, yshift = -0.2cm, xshift = 4cm ]{Assumptions not met};
\node(conf)[startstop, right of = test, xshift = 2 cm]{Confident};
\draw[arrow](assum) -- (fprop);
\draw[arrow](assum) -- (eprop);
\draw[arrow](eprop) -- (test);
\draw[arrow](test) -- \node[above]{Yes}(conf);
\draw[arrow](test) -- \node[left]{No}(theory);
\draw[arrow](test) -- \node[right]{No}(assump);
\end{tikzpicture}
\end{figure}
\end{document}