\begin{table}[!h]
\centering
\begin{tabular}[t]{>{}lrrrrrr}
\toprule
\multicolumn{1}{c}{ } & \multicolumn{3}{c}{Group 1} & \multicolumn{3}{c}{Group 2} \\
\cmidrule(l{3pt}r{3pt}){2-4} \cmidrule(l{3pt}r{3pt}){5-7}
  & mpg & cyl & disp & hp & drat & wt\\
\midrule
\textbf{Mazda RX4} & 21.0 & 6 & 160 & 110 & 3.90 & 2.620\\
\textbf{Mazda RX4 Wag} & 21.0 & 6 & 160 & 110 & 3.90 & 2.875\\
\textbf{Datsun 710} & 22.8 & 4 & 108 & 93 & 3.85 & 2.320\\
\textbf{Hornet 4 Drive} & 21.4 & 6 & 258 & 110 & 3.08 & 3.215\\
\textbf{Hornet Sportabout} & 18.7 & 8 & 360 & 175 & 3.15 & 3.440\\
\bottomrule
\end{tabular}
\end{table}