Variability estimator V_m versus L_opt,M,ε, and Ṁ for the simulated quasar sample. In each row, the left panel shows the input correlation in the basic sample, the other diagrams show the expected correlations in the “observed” simulated sample with density contours over-plotted. The two numbers close to the bottom of each panel are the slope (s) and the regression coefficient (r) from the linear regression (solid).