Distribution of data-quality-related biases in the line-width measurements. The left (right) panel shows the SE S/N as a function of the fractional difference between the coadded and SE FWHM (line dispersion, σ_l) of the C IV emission line. The vertical lines show the median velocity width difference of each histogram with the same color shown in Figure 5 and shown in the legend, and the length of the lines within the legend represents the HIPR range of each respective distribution.