\documentclass[tikz,border=2mm, convert]{standalone}
\usetikzlibrary{positioning,arrows.meta}

\begin{document}
\begin{tikzpicture}[>=Stealth, node distance=1.5cm]
    \node[circle, draw, minimum size=1cm] (A) {A};
    \node[circle, draw, minimum size=1cm, above left=1cm and 0.5cm of A] (C) {C};
    \node[circle, draw, minimum size=1cm, above right=1cm and 0.5cm of A] (D) {D};

    \draw[->] (A) -- (C) node[midway, anchor=south east, align=right, xshift=1mm, yshift=-5mm] {$\frac{1}{2}$};
    \draw[->] (A) -- (D) node[midway, anchor=south west, xshift=-1mm, yshift=-5mm] {$\frac{1}{2}$};
    \node[circle, draw, minimum size=1cm, below right=1cm and 0.5cm of D] (B) {B};
    \node[circle, draw, minimum size=1cm, above right=1cm and 0.5cm of B] (E) {E};
    \draw[->] (B) -- (D) node[midway, anchor=south east, align=right, xshift=1mm, yshift=-5mm] {$\frac{1}{4}$};
    \draw[->] (B) -- (E) node[midway, anchor=south west, xshift=-1mm, yshift=-5mm] {$\frac{3}{4}$};
    \node[circle, draw, minimum size=1cm, below right=1cm and 0.5cm of A] (Root) {R};
    \draw[->] (Root) -- (A) node[midway, anchor=south east, align=right, xshift=1mm, yshift=-5mm] {$\frac{1}{2}$};
    \draw[->] (Root) -- (B) node[midway, anchor=south west, xshift=-1mm, yshift=-5mm] {$\frac{1}{2}$};
\end{tikzpicture}
\end{document}