Metallicity differences Δlog(O/H) between SDSS and VIPERS mass-complete samples (top row) and between SDSS and VIPERS non-mass-complete samples (bottom row). Contours show the 1σ, 2σ, and 3σ levels of the MS distributions for the VIPERS subsamples. In the left panel, the M_⋆-SFR bins are color-coded according to the metallicity difference in unit of dex. In the right panel, the bins are color-coded according to the metallicity difference normalized by the 〈σ_med〉_VIPERS.