\begin{table}%t5
 \caption{Statistics on $z$ for both samples. The two distributions 
   are obviously very alike.\label{list_z}}
   %\centering
\par
 \begin{tabular}{llllll}
\hline  \hline
   Sample&Nb&$<z>$&$z$ min&$z$ max&$\sigma$\\
   name&of spect.&&&&\\
   \hline
   FSM&26&0.18&0.015&0.658&0.16\\
   IRAS&28&0.18&0.020&0.558&0.12\\
   \hline	
 \end{tabular}
\end{table}