X-ray observable diagram of the XXL C1 sample, integrated over the redshift range [0.05-1] used in this study, together with the 1D CR, HR distributions in blue. In red, the theoretical diagram predicted by our ΛCDM best-fit parameters given in section 4.1. We can see where the CR–HR space is not dominated by the shot noise ( objects); we obtain, on average, that is smaller than . Error bars only account for shot noise.