\begin{tabular}{*{3}{l}}
\hline
                  & \multicolumn{2}{c}{M1}   \tabularnewline
                   &Estimate  &(S.E.)  \tabularnewline
 \hline
 \hline
   (Intercept)     &-209.286***   &   (30.122) \tabularnewline
   xc              &-7.633***   &   ( 0.687) \tabularnewline
   xcsquare        &-0.061*   &   ( 0.027) \tabularnewline
 \hline
 N                 &400       &        \tabularnewline
 RMSE             &395.181         & \tabularnewline
 $R^2$             &0.240         & \tabularnewline
 adj $R^2$         &0.236         & \tabularnewline
 \hline
\hline
 
 \multicolumn{3}{c}{${*  p}\le 0.05$${*\!\!*  p}\le 0.01$${*\!\!*\!\!*  p}\le 0.001$}\tabularnewline
 \end{tabular}