\documentclass[10pt]{article}
\usepackage{color}
\usepackage{tikz}

% Tikz settings optimized for causal graphs.
% Just copy-paste this part
\usetikzlibrary{shapes,decorations,arrows,calc,arrows.meta,fit,positioning}
\tikzset{
    -Latex,auto,node distance =1 cm and 1 cm,semithick,
    state/.style ={ellipse, draw, minimum width = 0.7 cm},
    point/.style = {circle, draw, inner sep=0.04cm,fill,node contents={}},
    bidirected/.style={Latex-Latex,dashed},
    el/.style = {inner sep=2pt, align=left, sloped}
}
\begin{document}

\begin{tikzpicture}
    % x node set with absolute coordinates
    \node[state] (x) at (0,0) {$X$};

    % y node set relative to x.
    % Locations can be:
    % right,left,above,below,
    % above left,below right, etc
    \node[state] (y) [right =of x] {$Y$};

    % Directed edge
    \path (x) edge (y);

    % Bidirected edge
    \path[bidirected] (x) edge[bend left=60] (y);
\end{tikzpicture}
\end{document}