Richness-velocity dispersion scaling relation. The black solid line shows the best BCES orthogonal fit of the N_1  Mpc − σ_SIS relation using the SARCS most secure candidates (red points) and adding the EXCPRES galaxy clusters of Foëx et al. (2012) (blue open triangles). The grey shaded area gives the statistical 1σ uncertainty given by the best fit parameters (statistical dispersion σ_stat). The red line (and corresponding shaded area) is the best fit using only the SARCS most secure candidates.