\begin{table}%T7
\caption{{\it HR}2 statistic for some relevant BSS and HBSS sub-sample(s).}\label{t7}
%\centerline
{
\begin{tabular}{lrrrrrr}
\hline
\hline
Sample               & Objects    & Weighted             & Unweighted         & Median   & St.Dev.   & $\sigma$ intrins.  \\
(1)                  & (2)        & (3)                  & (4)                & (5)      & (6)       & (7)                \\
\hline
BSS Sample:          &            &                      &                    &          &           &                \\
\ \ Extragalactic    &  333       & $-$0.51 $\pm$ 0.01     & $-$0.54 $\pm$ 0.01   & $-$0.57    &  0.20     & 0.16            \\
\ \ \ \~AGN1         &  180       & $-$0.54 $\pm$ 0.01     & $-$0.56 $\pm$ 0.01   & $-$0.58    &  0.15     & 0.12            \\
\ \ \ \~AGN2         &   26       & $-$0.32 $\pm$ 0.07     & $-$0.34 $\pm$ 0.07   & $-$0.49    &  0.35     & 0.32            \\
\ \ \ \ Unidentified &  111       & $-$0.52 $\pm$ 0.02     & $-$0.54 $\pm$ 0.02   & $-$0.56    &  0.16     & 0.12            \\
\ \ Stars            &   56       & $-$0.83 $\pm$ 0.01     & $-$0.88 $\pm$ 0.01   & $-$0.90    &  0.11     & 0.08            \\
HBSS Sample:         &            &                      &                    &          &           &                \\
\ \ Extragalactic    &   65       & $-$0.10 $\pm$ 0.05     & $-$0.27 $\pm$ 0.05   & $-$0.47    &  0.44     & 0.40            \\
\ \ \ \~AGN1         &   39       & $-$0.44 $\pm$ 0.03     & $-$0.49 $\pm$ 0.03   & $-$0.53    &  0.21     & 0.18            \\
\ \ \ \~AGN2         &   16       &  0.14 $\pm$ 0.11     &  0.05 $\pm$ 0.11   & $-$0.02    &  0.45     & 0.44            \\
\hline
\end{tabular}}
\par
\medskip
Columns are as follows:
(1) Sample;
(2) Number of sources;
(3) {\it HR}2 weighted average;
(4) {\it HR}2 unweighted average;
(5) {\it HR}2 median value;
(6) Observed standard deviation of the {\it HR}2 distribution;
(7) Intrinsic dispersion of the {\it HR}2 distribution computed
using the maximum likelihood method as described in
Maccacaro et~al. (\cite{Maccacaro88}).
\end{table}