Spectroscopic success rate (SSR) as a function of different observed photometric properties (blue solid curve), compared to the result of applying the weight to correct incompleteness (red solid curve). The two rows of plots show how the completeness correction changes when one only considers a simple SSR dependence on the selection i-band magnitude (top), or rather includes the more subtle dependencies on observed colours and, in particular, quality of the specific VIMOS quadrant (“Q” parameter, quantified via the mean SSR for all galaxies in that quadrant). The differential distribution of each parameter is also plotted in each panel (dashed curve).