based on the most reliable data. Many of the SDSS average spectra are still quite noisy, so we imposed quality cuts. Even though we are for the most part restricting our attention to the SDSS-RM quasars for which there are measured lags for  (44 quasars) or  (48 quasars), we impose these cuts on the entire sample for the sake of later discussion. The first quality condition is that $$\label{eq:minwidth}
V \geq 1000\,{\mbox{\rm km~s$^{-1}$}}$$ for both $V = {\mbox{${\rm FWHM}_{\rm M}$}}$ and $V ={\mbox{$\sigma_{\rm M}$}}$, since AGNs with lines narrower than 1000  are probably Type 2 AGNs; there are some Type 1 AGNs with line widths narrower than this, including several in Table A1, but these are low-luminosity AGNs [e.g., @Greene07], not SDSS quasars. The second quality condition is that the best fit value $V({\rm BF})$ must lie in the range $$\label{eq:consistency}
\langle V \rangle - \Delta V \leq V({\rm BF}) \leq \langle V \rangle + \Delta V$$ for both FWHM and . A third quality condition is a “signal-to-noise” ($S/N$) requirement that the line width must be significantly larger than its uncertainty. Some experimentation showed that $$\label{eq:s2n}
\frac{V}{\Delta V} \geq 10$$ is a good criterion for both $V = {\mbox{${\rm 