an enlongated cloud of points whose axis is roughly parallel to the Eddington ratio when  is used to characterize the line width. However, when FWHM is used, the axis of the distribution rotates as the higher masses are underestimated and the lower masses are overestimated. However, the apparent rotation of the mass distribution is in the same sense that is expected from the Malmquist bias and a bottom heavy quasar mass function [@Shen13]. Unfortunately, these arguments are not statistically compelling. Examination of the –$\sigma{*}$ relation using FWHM-based and -based masses is equally unrevealing [@Wang19].

In reverberation mapping, a further distinction among line-width measures must be drawn since either FWHM or  can be measured in the mean spectrum, $$\overline{F}(\lambda) =\frac{1}{N} \sum_{1}^{N} F_i(\lambda),
\label{eq:meanspec}$$ where $F_i(\lambda)$ is the flux in the $i^{th}$ spectrum of the time series at wavelength $\lambda$ and $N$ is the number of spectra, or they can be measured in the rms residual spectrum (hereafter simply “rms spectrum”), which is defined as $$\sigma_{\rm rms}(\lambda) = \left\{ \frac{1}{N-1}
\sum_{1}^{N}\left[ F_i(\lambda) -
\overline{F}(\lambda)\right]^2 \right\}^{1/2}.
\label{eq:rmsspec}$$ In this paper, we will specifically refer to the measurements of  in the mean spectrum as  and in the rms spectrum as . Similarly,  refers to 