\begin{tabular}{*{3}{l}}
\hline
                  & \multicolumn{2}{c}{M1}   \tabularnewline
                   &Estimate  &(S.E.)  \tabularnewline
 \hline
 \hline
   (Intercept)     &-2.752   &   (4.794) \tabularnewline
   x1              &0.227***   &   (0.066) \tabularnewline
   x2              &0.211***   &   (0.061) \tabularnewline
 \hline
 N                 &100       &        \tabularnewline
 RMSE             &6.151         & \tabularnewline
 $R^2$             &0.184         & \tabularnewline
 adj $R^2$         &0.167         & \tabularnewline
 \hline
\hline
 
 \multicolumn{3}{c}{${*  p}\le 0.05$${*\!\!*  p}\le 0.01$${*\!\!*\!\!*  p}\le 0.001$}\tabularnewline
 \end{tabular}