\begin{table}%t4
\caption{Sensitivities of abundance ratios to variations in the atmospheric
parameters and to errors in the equivalent widths, as computed for a~typical 
program star with $T_{\rm eff} \sim 4750$~K. 
The total error is computed as the quadratic sum
of the three~dominant sources of error, $T_{\rm eff}$, $v_{\rm t}$ and errors in the {\it EW}s, scaled to the actual errors as described in the text (Col.~8: tot.1) or as the sum
of all contributions (Col.~9: tot.2).}\label{t:sensitivity}
%\centering
\small
\begin{tabular}{lrrrrrrrr}
\hline \hline
Ratio    & $\Delta T_{\rm eff}$ & $\Delta$ $\log g$ & $\Delta$ [A/H] & $\Delta v_{\rm t}$
&$\langle N_{\rm lines} \rangle$& $\Delta$ {\it EW} & tot.1 & tot.2\\
         & (+50 K)    & (+0.2 dex)      & (+0.10 dex)      & (+0.10 km~s$^{-1}$) & & & (dex)& (dex)  \\
 (1) & (2) & (3) & (4) & (5) & (6) & (7) & (8) & (9) \\
\hline
$[$Fe/H$]${\sc  i} &  +0.063 & $-$0.007 &$-$0.009 & $-$0.025 & 23 &+0.020  &0.039 &0.039  \\
$[$Fe/H$]${\sc ii} &$-$0.024 &   +0.085 &  +0.023 & $-$0.010 &  2 &+0.068  &0.069 &0.070  \\
\hline
$[$O/Fe$]$         &$-$0.046 &   +0.088 &  +0.026 &   +0.023 &  1 &+0.096  &0.101 &0.102  \\
$[$Na/Fe$]$        &$-$0.023 & $-$0.029 &$-$0.004 &   +0.018 &  3 &+0.055  &0.060 &0.060  \\
\hline
\end{tabular}
\end{table}