Effects of variations in mass and positions of groups. The dotted line corresponds to the groups with an artificial Gaussian dispersion around the simulated halo masses and the dashed line shows the HOD of groups using the brightest galaxy as centre. The solid line is the HOD of groups in the mock, with geometric centre and masses taken from the simulation, as in previous plots. Errors are determined using a standard jackknife procedure. These results correspond to M_lim = −19.0. The bottom panel shows the quotient between the HOD estimations.