\begin{table}%t7
\caption{{\bf a)} Parameters of the linear fits $I'=a+b\;\log\sigma$. First column:
$y$-intersect of the fit and its error; second column: slope, and corresponding
error, of the linear fit; $\alpha$: probability, given by a non-parametric
Spearman test, that the slope of the fit is significatively different from zero
by chance; $N$: number of galaxies used to make the fit; $t$: $t$ parameter to
test the hypothesis $b=0$ (a $t$ value higher than 1.9 indicates that 
the slope
is significant different from zero with a significance level lower than
0.05); $\sigma_{\rm std}$: standard deviation about the fit; $\sigma_{\exp}$:
standard deviation expected from the errors; $\sigma_{\rm res}$: standard
deviation not explained from the errors.\label{tabla-relaciones}}
%\centering
\par
\small
\begin{tabular}{@{}lrrrrrrrr@{}}
\hline\hline
                \multicolumn{9}{c}{LDEGs}\\
\hline
  Index        & \multicolumn{1}{c}{$a\pm\sigma(a)$}&\multicolumn{1}{c}{$b\pm\sigma(b)$}&\multicolumn{1}{c}{$\alpha$}&
 \multicolumn{1}{c}{$N$}
  &\multicolumn{1}{c}{$t$}&\multicolumn{1}{c}{$\sigma_{\rm std}$}&
 \multicolumn{1}{c}{$\sigma_{\rm exp}$}&\multicolumn{1}{c}{$\sigma_{\rm res}$}\\
\hline
D4000$'$       &$ 0.484\pm0.016$  &$ 0.1679\pm0.007$    &0.005  & 59& 23.98 & 0.037 &0.012& 0.035\\
H$\delta'_A$   &$ 0.050\pm0.023$  &$-0.049\pm0.004$    &9.22E-07& 59&  4.83 & 0.032 &0.002& 0.032\\
H$\delta'_F$   &$ 0.126\pm0.016$  &$-0.052\pm0.007$    &1.72E-09& 59&  7.66 & 0.038
&0.002& 0.038\\
CN$_2$         &$-0.276\pm0.035$  &$ 0.178\pm0.007$    &3.08E-17& 59& 12.96 & 0.023 &0.006&
0.023\\
Ca4227$'$      &$ 0.033\pm0.011$  &$ 0.027\pm0.005$    &5.93E-06& 59&  2.20 & 0.008 &0.004&
0.007\\ 
G4300$'$       &$ 0.130\pm0.008$  &$ 0.017\pm0.004$    &0.054  & 59&  1.96 & 0.017 &0.003& 0.017\\
H$\gamma'_A$   &$-0.004\pm0.010$  &$-0.056\pm0.004$    &4.16E-09& 59&  6.52 & 0.026 &0.002&
0.026\\
H$\gamma'_F$   &$ 0.157\pm0.013$  &$-0.097\pm0.006$    &9.65E-11& 59&  9.85 & 0.025 &0.004&
0.025\\
Fe4383$'$      &$ 0.054\pm0.007$  &$ 0.026\pm0.003$   &2.97E-08& 59&  3.20 & 0.009 &0.002& 0.009\\  
Ca4455$'$      &$ 0.023\pm0.008$  &$ 0.024\pm0.003$    &3.61E-07& 59&  2.51 & 0.004 &0.003&
0.002\\
Fe4531$'$      &$ 0.051\pm0.007$  &$ 0.015\pm0.003$    &2.53E-07& 59&  3.18 & 0.003 &0.002&
0.003\\   
C4668$'$       &$-0.032\pm0.001$  &$ 0.054\pm0.004$    &2.23E-09& 59&  7.34 & 0.009 &0.003&
0.009\\
H$\beta$'      &$ 0.130\pm0.014$  &$-0.030\pm0.006$    &1.37E-09& 59&  5.25 & 0.012 &0.002&
0.012\\
Fe5015$'$      &$ 0.048\pm0.005$  &$ 0.013\pm0.002$    &1.0E-04  & 59&  2.30 & 0.004 &0.002&
0.004\\
Mgb$'$         &$-0.073\pm0.012$  &$ 0.100\pm0.005$    &1.22E-16& 59& 10.78 & 0.011 &0.002& 0.011\\
Fe5270$'$      &$ 0.047\pm0.010$  &$ 0.016\pm0.004$    &0.001  & 59&  3.60 & 0.004 &0.002& 0.004\\
Fe5335$'$      &$ 0.029\pm0.013$  &$ 0.020\pm0.006$    &0.030  & 59&  3.52 & 0.003 &0.003& 0.000\\
  %             &                    &                      &        &   &       &        &      &       \\
\hline
\end{tabular}
%\vspace{4mm}
%\end{table}