Average X-ray and UV spectral properties of the SDSS-XMM and SDSS-Chandra sub-samples in the z = 3.0–3.3 redshift range. Upper panel: stacked X-ray emission (black data point); its power-law model photon index Γ = 1.89 ± 0.02 is perfectly compatible with the average value of Γ = 1.9 of ‘typical’ unobscured quasars (Reeves & Turner 2000; Risaliti et al. 2009; Scott et al. 2011) shown by the solid red line. Lower panel: stacked SDSS spectrum (solid black line) compared with the average quasar spectrum (solid red line) from a large sample of SDSS quasars over a wide redshift and luminosity range (Vanden Berk et al. 2001).