%%% requires use of multirow package: include the following in the
%%% preamble:

\usepackage{multirow}

%%%% snippet to generate table in the assignment


\begin{center}
\begin{Large}
\begin{tabular}{|r||l|l||l|l|} \hline
 & \multicolumn{2}{|c||}{$N=900$} & \multicolumn{2}{|c|}{$N=2500$} \\
 & \%-Sim & Ticks & \%-Sim & Ticks \\ \hline\hline
\multirow{3}{*}{$t = 20\%$}
   & Avg.\hspace*{2cm} & Avg.\hspace*{2cm}
   & Avg.\hspace*{2cm} & Avg. \hspace*{2cm} \\ [5mm]
 & Min.\ & Min.\ & Min.\ & Min.\  \\ [5mm]
 & Max.\ & Max.\ & Max.\ & Max.\  \\ [5mm] \hline
\multirow{3}{*}{$t = 30\%$}
   & Avg.\hspace*{2cm} & Avg.\hspace*{2cm}
   & Avg.\hspace*{2cm} & Avg. \hspace*{2cm} \\ [5mm]
 & Min.\ & Min.\ & Min.\ & Min.\  \\ [5mm]
 & Max.\ & Max.\ & Max.\ & Max.\  \\ [5mm]\hline
\multirow{3}{*}{$t = 55\%$}
   & Avg.\hspace*{2cm} & Avg.\hspace*{2cm}
   & Avg.\hspace*{2cm} & Avg. \hspace*{2cm} \\ [5mm]
 & Min.\ & Min.\ & Min.\ & Min.\  \\ [5mm]
 & Max.\ & Max.\ & Max.\ & Max.\  \\ [5mm]\hline
\end{tabular}
\end{Large}
\end{center}