  This work studies the relationship between accretion-disk size and quasar
properties, using a sample of 95 quasars from the SDSS-RM project with measured
lags between the $g$ and $i$ photometric bands. Our sample includes disk lags
that are both longer and shorter than predicted by the \citet{SS73} model,
requiring explanations which satisfy both cases. Although our quasars each have
one lag measurement, we explore the wavelength-dependent effects of diffuse
broad line region (BLR) contamination through our sample's broad redshift
range, $0.1<z<1.2$. We do not find significant evidence of variable diffuse
\FeII\ and Balmer nebular emission in the root-mean-square (RMS) spectra, nor
from Anderson-Darling tests of quasars in redshift ranges with and without
diffuse nebular emission falling in the observed-frame filters. Contrary to
previous work, we do not detect a significant correlation between measured
continuum and BLR lags in our luminous quasar sample, similarly suggesting that
our continuum lags are not dominated by diffuse nebular emission. Similar to
other studies, we find that quasars with larger-than-expected continuum lags
have lower 3000~\AA\ luminosity, and we additionally find longer continuum lags
with lower X-ray luminosity and black hole mass. Our lack of evidence for
diffuse BLR contribution to the lags indicates that the anti-correlation
between continuum lag and luminosity is not likely to be due to the Baldwin
effect. Instead, these anti-correlations favor models in which the continuum
lag increases in lower-luminosity AGN, including scenarios featuring magnetic
coupling between the accretion disk and X-ray corona, and/or ripples or rims in
the disk.
