Location of the AGBb in log ν_max (left) and in log T_eff (right) from observations, as a function of the metallicity, [Fe/H]. The AGBb occurrence is marked by dots and the stellar mass is colour-coded. AGBb locations obtained in the same bin of mass, M ∈ [0.6, 0.9], [0.9, 1.2], [1.2, 1.5], [1.5, 2.5] M_⊙ are connected by dark blue, light blue, light green, and red lines, respectively. Mean error bars on the location of the AGBb in log ν_max and in log T_eff are shown in black. Data in the bin M ∈ [0.6, 0.9] M_⊙; [Fe/H] ∈ [0, 0.25] dex are not shown because there are not enough stars to perform the statistical mixture model.