The α_OX vs. luminosity compared with (1) the average values found by Yuan et al. (1998) for a sample of ~1000 optically selected quasars (gray lines), (2) the average α_OX of PG quasars (dashed line), and (3) the average α_OX of X‐ray–selected quasars, according to Elvis et al. 1994 (bottom solid line). The three low‐luminosity objects are those with Chandra fluxes significantly higher than ROSAT upper limits.