Uncorrected and corrected frequency differences between observed frequencies for the degraded solar data and MESA models fit using only the cubic term (Eq. (3)). The solid and empty points show the uncorrected and corrected differences with error bars that correspond to the observed uncertainties. The shaded regions show the spread of the modelled frequencies. i.e. taken from the 100 fits to random realizations of the observations. There is no obvious remaining trend in the corrected frequencies.