Upper: variance σ_g,R = ξ_g,R(0) of the SDSS LRG sample as a function of the filtering scale R for 2 different sets: the full sample (diamonds) and the subsample containing the brightest 50% (in the r band). Middle: the correlation function ξ_g,R(3R) of the smoothed galaxy density field is shown as a function of R for the same subsets. Both the variance and the correlation function are estimated in the best-fitting cosmological model. Lower: the amplitude of the galaxy clustering ratio η_g,R(3R) is demonstrated to be the same for these two samples of biased tracers of the large scale distribution of matter. Also shown is the theoretically predicted scaling of the mass clustering ratio (dot-dashed line). This last quantity is computed assuming the best-fitting cosmological parameters p^f = (0.28, 0.45, −1.2, 73.8, 0.0213, 0.96) deduced from analysis of the whole LRG sample on the specific scale R = 14  h^-1 Mpc. In all panels, error bars are derived from 30 block-jackknife resampling of the data, excluding, each time, a sky area of 12×14 deg².