Subtitle in table

Question

I have a table of the form

\documentclass[12pt,a4paper]{article} % 
\begin{document}    
\begin{table}
\begin{center}
\caption{\centering How many people \\
 \scriptsize     Average over a thousand simulations}
\label{table1}
\begin{tabular}{llll}
 $r \backslash 2n$  & 100 & 200& 1000\\
 \hline\\
 2 & 25.42 & 25.76 &25.47\\
 \hline
 \end{tabular}
 \end{center}
 \end{table}
\end{document}

My question is that here I have a nice subtitle, that looks great but that gives me errors when running it. Is there a way to take away the errors but make it look exactly the same? I really don't like \tablenotes.

EDIT: the error I am getting is

 Argument of \caption @ydblarg has an extra }

Answer 1

So, by loading the caption package, I obtain a solution:

\documentclass[12pt,a4paper]{article} % 
\usepackage{caption}
\begin{document}    
\begin{table}
\centering
\caption{ How many people \\ 
\scriptsize  Average over a thousand simulations}
\label{table1}
\begin{tabular}{llll}
 $r \backslash 2n$  & 100 & 200& 1000\\
 \hline\\
 2 & 25.42 & 25.76 &25.47\\
 \hline
 \end{tabular}
 \end{table}
\end{document}