Gaussian Function aka Bell curve

You can use pgfplots to plot your own functions. There’s no standard macro for it, but the function isn’t too complicated and can be added as a pgfmath function.

This code was written by Jake on TeX.SE.

Bell curve

\documentclass[border=10pt]{standalone}
\usepackage{pgfplots}
\pgfplotsset{width=7cm,compat=1.8}
\pgfmathdeclarefunction{gauss}{2}{%
  \pgfmathparse{1/(#2*sqrt(2*pi))*exp(-((x-#1)^2)/(2*#2^2))}%
}
\begin{document}
\begin{tikzpicture}
\begin{axis}[every axis plot post/.append style={
  mark=none,domain=-2:3,samples=50,smooth},
    % All plots: from -2:2, 50 samples, smooth, no marks
  axis x line*=bottom, % no box around the plot, only x and y axis
  axis y line*=left, % the * suppresses the arrow tips
  enlargelimits=upper] % extend the axes a bit to the right and top
  \addplot {gauss(0,0.5)};
  \addplot {gauss(1,0.75)};
\end{axis}
\end{tikzpicture}
\end{document}
Click to download: bell-curve.texbell-curve.pdf