\begin{table}%t4
\caption{Statistical comparison of the abundances of 15~elements for cluster and field $\delta$~Scuti stars.}
\label{TAB t-test}
\par
\small%\centerline
 {
\begin{tabular}{rrrrrrrrrrr}
\hline
\hline
 &\multicolumn{3}{c}{Cluster}& &\multicolumn{3}{c}{Field}& & $t$ & Pr \\
El.&\# &mean   &rms   & &\# &mean   &rms   & &       &      \\
\hline
C  &$7$&$+0.22$&$0.28$& &$6$&$+0.10$&$0.30$& &$0.753$&$0.467$\\
O  &$4$&$-0.02$&$0.33$& &$2$&$-0.07$&$0.23$& &$0.196$&$0.854$\\
Na &$7$&$+0.12$&$0.41$& &$3$&$+0.21$&$0.25$& &$0.346$&$0.738$\\
Mg &$8$&$-0.06$&$0.40$& &$7$&$+0.11$&$0.33$& &$0.858$&$0.407$\\
Si &$8$&$+0.22$&$0.33$& &$7$&$-0.02$&$0.26$& &$1.511$&$0.155$\\
S  &$5$&$+0.47$&$0.29$& &$7$&$+0.36$&$0.30$& &$0.672$&$0.517$\\
Ca &$8$&$+0.12$&$0.40$& &$7$&$+0.11$&$0.29$& &$0.092$&$0.928$\\
Sc &$8$&$+0.16$&$0.43$& &$7$&$+0.04$&$0.29$& &$0.605$&$0.556$\\
Ti &$8$&$+0.17$&$0.34$& &$7$&$+0.26$&$0.27$& &$0.572$&$0.577$\\
Cr &$7$&$+0.04$&$0.31$& &$7$&$+0.04$&$0.37$& &$0.016$&$0.988$\\
Mn &$7$&$+0.02$&$0.37$& &$4$&$+0.25$&$0.28$& &$1.120$&$0.292$\\
Fe &$8$&$+0.08$&$0.30$& &$7$&$+0.08$&$0.31$& &$0.001$&$0.999$\\
Ni &$8$&$+0.09$&$0.37$& &$6$&$-0.09$&$0.34$& &$0.916$&$0.378$\\
Y  &$7$&$+0.39$&$0.34$& &$6$&$+0.36$&$0.30$& &$0.210$&$0.838$\\
Ba &$8$&$+0.32$&$0.39$& &$7$&$+0.55$&$0.34$& &$1.179$&$0.260$\\
\hline
   &$108$&     &      & &$90$&      &      & &$0.060$&$0.952$\\
\hline
\end{tabular}}
\medskip 
For each element, the number of stars, the mean abundance, and the standard 
error is given. The last two columns represent the $t$~values for a paired Student test and the 
resulting probabilities~(Pr) that the two samples are taken from the same statistical population. The bottom row refers to the overall statistics for all elements.
\end{table}