\begin{table}%t6
%\centering
\par
\caption{Comparison of line strengths measured in this and other studies. Ref.:
reference of the comparison work (see description in the text); $N$: number of
galaxies in common; $\Delta I$: calculated offset between both studies (this work minus
other study); $\sigma$: rms\ dispersion; $\sigma_{\rm exp}$:
expected rms\ from the errors; $t$: $t$-parameter of the comparison of
means; $\alpha$: probability that $\sigma > \sigma_{\rm exp}$ by chance.
\label{tab.comparison.oa}}
%\centering
\par
\small
\begin{tabular}{@{}lccccccc@{}}
\hline\hline
Index    &  Ref. &  $N$  & $\Delta I$ & $\sigma$  & $\sigma_{\rm exp}$ & $t$& $\alpha$\\
\hline
H$\delta_A$&D05   &  24         &  +0.305    &  0.442    & 0.569             & 2.76 & 0.006\\
H$\delta_F$&D05   &  24         & $-0.036$   &  0.197    & 0.450              & 0.87 & 0.197\\ 
H$\gamma_A$&D05   &  24         &  +0.550    &  0.428    & 0.555              & 3.82 & 0.001\\
H$\gamma_F$&D05   &  24         &  +0.349    &  0.359    & 0.463              & 3.38 & 0.001\\
CN$_2$   &  T98  &  53          & $-0.010$   &  0.033    & 0.195              & 2.22  & 0.015  \\ 
CN$_2$   &  D05  &  24          &  +0.125    &  0.034    & 0.094              & 4.64 & 0.001\\
Ca4427   &  T98  &  53          & $-0.181$   &  0.287    & 0.755              & 3.88 & 0.001\\
Ca4227   &  D05  &  24          & $-0.070$   &  0.170    & 0.341              & 1.85 & 0.039\\
G4300    &  T98  &  53          & $-0.272$   &  0.640    & 0.807              & 2.84 & 0.003\\
G4300    &  D05  &  24          &  +0.061    &  0.310    & 0.506              & 0.94 & 0.179\\
Fe4383   &  T98  &  53          &$-0.051$    &  0.561    & 1.081              & 0.65 & 0.259    \\
Fe4383   &  D05  &  24          & $-0.639$   &  0.463    & 0.615              & 3.91 & 0.001\\
Ca4455   &  T98  &  53          & $ -0.150$  &  0.304    & 0.700              & 3.21 & 0.001    \\
Ca4455   &  D05  &  24          &  +0.170    &  0.210    & 0.419              & 3.05 & 0.003\\
Fe4531   &  T98  &  53          & $-0.205$   &  0.422    & 0.887              & 3.18 & 0.001    \\
Fe4531   &  D05  &  24          & $-0.175$   &  0.217    & 0.411              & 3.05 & 0.003\\
C4668    &  T98  &  53          & $-0.667$   &  0.821    & 1.129              & 4.57 & 0.001   \\ 
C4668    &  M02  &  12          & $-1.194$   &  1.332    & 1.143              & 2.19 & 0.027 \\
C4668    &  D05  &  24          & $-0.684$   &  0.541    & 0.671              & 3.79 & 0.001\\
H$\beta$ &  T98  &  53          & +0.121     &  0.256    & 0.621              & 3.10 & 0.001  \\
H$\beta$ &  G93  &  33          & $-0.057$   &  0.150    & 0.333              & 2.16 & 0.019   \\
H$\beta$ &  K01  &  32          &+0.098      &  0.187    & 0.565              & 2.62 & 0.007     \\
H$\beta$ &  M00  &  6           & $-0.428$   &  0.316    & 0.418              & 1.86 & 0.068\\
H$\beta$ &  D05  &  24          & +0.004     &  0.491    & 0.357              & 0.04 & 0.484\\
Fe5015   &  T98  &  53          &$-0.187$    &  1.030    & 0.739              & 1.79 & 0.040  \\
Fe5015   &  G93  &  33          & $-0.451$   &  0.465    & 0.612              & 2.22 & 0.017    \\
Fe5015   &  D05  &  24          & $-0.208$   &  0.653    & 0.574              & 1.48 & 0.076\\
Mgb      &  T98  &  53          &$-0.376$    &  0.478    & 0.717              & 4.49 & 0.001  \\
Mgb      &  G93  &  33          &$-0.535$    &  0.601    & 0.386              & 2.20 & 0.018\\
Mgb      &  K01  &  32          &$-0.047$    &  0.431    & 0.615              & 0.61 & 0.273     \\
Mgb      &  M00  &   6          &$-0.158$    &  0.220    & 0.491              & 1.39 & 0.118\\
Mgb      &  M02  &  12          & $-0.160$   &  0.125    & 0.518              & 2.66 & 0.012\\
Mgb      &  D05  &  24          & +0.061     &  0.443    & 0.467              & 0.67 & 0.255\\
Fe5270   &  T98  &  53          & +0.009     &  0.340    & 0.761              & 0.19 & 0.425  \\
Fe5270   &  G93  &  33          & +0.004     &  0.027    & 0.322              & 0.61 & 0.273\\
Fe5270   &  M00  &   6          & +0.212     &  0.153    & 0.480              & 1.87 & 0.067\\
Fe5270   &  M02  &  12          & +0.118     &  0.213    & 0.495              & 1.66 & 0.064\\
Fe5270   &  D05  &  24          & $-0.057$   &  0.181    & 0.399              & 1.46 & 0.079\\
Fe5335   &  T98  &  53          &+0.009      &  0.340    & 0.761              & 0.19 & 0.425 \\
Fe5335   &  G93  &  33          &$-0.009$    &  0.018    & 0.340              & 1.79 & 0.042\\
Fe5335   &  M00  &   6          &+0.111      &  0.398    & 0.514              & 0.65 & 0.275\\ 
Fe5335   &  M02  &  12          &+0.035      &  0.373    & 0.598              & 0.32 & 0.378\\ 
Fe5335   &  D05  &  24          &+0.040      &  0.431    & 0.441              & 0.45 & 0.328\\
$<$Fe$>$ &  K01  &  31          &$-0.016$    &  0.183    & 0.159              & 0.65 & 0.110\\
\hline
\end{tabular}
\end{table}