Completeness functions compared to the distribution of the selected clusters in the M₂₀₀ − z plane (black points). The full lines plot the true value of mass (see text and Appendix A in Sereno & Ettori 2015b for details) below which a given fraction (from top to bottom: 85, 50, and 15 per cent levels, respectively) of the selected sample is contained. The shaded green region encloses the 68.3 per cent confidence region around the 50 per cent level due to uncertainties on the parameters.