Individual scaled SZ signal measurements, , for the MaxBCG catalogue as a function of richness N₂₀₀. We do not plot individual error bars to avoid saturating the figure. The error bar drawn in the upper left represents the median uncertainty over the entire population; in general, the uncertainty increases towards low richness. The SZ signal measurements are expressed as the Compton y parameter integrated over a sphere out to R₅₀₀, scaled in redshift according to the self-similar model and placed at a fiducial angular distance of 500 Mpc. Each point represents the result of the matched filter applied to an individual cluster in the catalogue. Upward pointing arrows indicate values beyond the plotted range. The radius R₅₀₀, and hence the filter size, is set from the mass of each cluster determined via the weak-lensing calibrated M₅₀₀ − N₂₀₀ relation given by Johnston et al. (2007). The results are nearly the same for the relation given by Rozo et al. (2009).