Top panel: scatter of the F_disc − F_cor relation as a function of a cut in the ratio between the total (source plus background) and background-only 10 − 25 keV count rates. Coloured points are relative to the full sample and coded with the 16th–84th interquantile range in the related Γ distributions, whereas grey points are obtained excluding SS10. Stars correspond to the starting sample with no filters. Bottom panel: scatter as a function of a cut in the fraction of time spent by GX 339–4 in a region of the outburst, including SSs and SIMSs only (see Sect. 4.2 for a detailed description). Colour coding and symbols are the same as in the top panel.