Redshift uncertainty Δz (defined as |z_out − z_in|) for the total sample of 2496 AGN as a function of the parameter R_xcorr (which is related to the shape of the correlation peak, and is inversely proportional to the redshift measurement uncertainty) when using no prior (upper panel) and a photometric redshift prior (lower panel). Different colours refer to different classifications of the redshift estimates (see Sect. 5 for more details).