Comparison of the σ_{Fe Kα}/σ_c slopes with respect to (a) SMBH M_BH, (b) Eddington ratio, (c) line-of-sight column density, (d) radio-loudness, and (e) AGN type. For the first five plots, the thick red line denotes the best-fit linear regression, while thin red lines denote fits from Monte Carlo resampling to estimate uncertainties; the best-fit slope and error are indicated in the legend of each plot.