Clustering ratio η_g,R estimated from L_h haloes in real space (diamonds) is shown as a function of the filtering radius R and of the correlation length r = 3R. We also plot the clustering ratio estimated after perturbing the cosmological redshift of haloes with random errors (triangles). These random velocities are drawn from a Gaussian distribution with standard deviation σ_cz = (1 + z)σ_u km s^-1 with σ_u as indicated. Also shown is the theoretically predicted value of obtained by inserting into Eq. (8) the corresponding value of σ_u. The points and error bars correspond to the average and standard deviation of the mean of the measurements over 31L_h catalogues. Such error bars, in practice, would correspond to the typical uncertainty in a survey with 31 times larger volume and 10 times higher galaxy number density than the VIPERS W4 sample.