Ratio between the estimated and actual masses of simulated groups with total number of members and velocity dispersions similar to the ones measured for SL2SJ02140-0535, i.e. number of members between 20 and 40, and velocity dispersion between 260 and 460 km s^-1. The number of groups in each bin of the plot remains constant. The x-axis corresponds to the fraction of members used for calculating the group mass.