Table 1: Summary of the error budget for the $EW_{w}\{{\rm Si}~{\rm II}\}$ measurements.
Source Size

statistical error $15{-}27\%$ (low-z vs. high-z)

galaxy contamination < $20{-}40\%$ (E vs. S type)

low S/N < $5\%$ for ${\it S/N} \geq5$

reddening < $0.5\%$

high frequency feature residuals < $0.5\%$

**Table 1:** Summary of the error budget for the $EW_{w}\{{\rm Si}~{\rm II}\}$ measurements.
Source	Size
statistical error	$15{-}27\%$ (low-z vs. high-z)
galaxy contamination	< $20{-}40\%$ (E vs. S type)
low S/N	< $5\%$ for ${\it S/N} \geq5$
reddening	< $0.5\%$
high frequency feature residuals	< $0.5\%$

Source LaTeX | All tables | In the text