Difference (Delta) between APOGEE determinations of [Fe/H] and those from the reference catalogues versus magnitude, T_eff, log g, and [Fe/H]. The upper panel is for the literature mean value from PASTEL, the middle panel for OC members with cluster mean metallicities from Netopil et al. (2016), and the bottom panel for GC members with cluster mean metallicities from Harris (2010). The colour code reflects the metallicity uncertainty, quadratically combined for APOGEE versus PASTEL, from APOGEE only for the clusters (note the different scales).