Evolution with the central hydrogen content of the differences of frequency at maximum power, ν_max, between models without and with g_rad for the three grids (upper panels). The same, but for the average large separation Δν₀ (lower panels). Each colour corresponds to a given mass. The dashed lines represent the same models but without the effect of partial ionisation. The horizontal black dash-dotted lines indicate the adopted A uncertainty set, and the horizontal black dashed lines indicate the adopted B uncertainty set on ν_max (upper panels) and Δν₀ (lower panels).