\begin{table}%T1
\caption{\label{errorsummary}Summary of the error budget for the
$EW_{w}\{{\rm Si}~{\rm II}\}$ measurements.}
\small%\centering
\par
\begin{tabular}{ll}
 \hline \hline
 Source & Size \\ 
 \hline 
statistical error & $15{-}27\%$ (low-$z$ vs. high-$z$) \\
galaxy contamination & $<$$20{-}40\%$ (E vs. S type)\\
low {\it S/N} & $<$$5\%$ for ${\it S/N} \geq5$ \\
reddening & $<$$0.5\%$ \\
high frequency feature residuals & $<$$0.5\%$ \\
\hline
\end{tabular}
\end{table}