Fits of Eq. (1) to the second differences of the mean CoRoT frequencies for HD 49933 and the histograms for the fitted values of τ_HIZ and τ_BCZ for different realisations of the data for different subsets (corresponding to different choices of ℓ values). The second differences of the frequencies of ℓ = 0 (blue), ℓ = 1 (red) and ℓ = 2 (green) modes of HD 49933 and their fit to Eq. (1) (magenta curve) are shown in the left panel. The dotted cyan line in the bottom left panel shows the fit by the Houdek & Gough (2007) form. The corresponding histograms of the fitted values of τ_BCZ (in red) and τ_HIZ (in blue) for different realisations are shown in the right panel. N denotes the total number of valid realisations after rejecting fits with τ_BCZ > 2700 s. The solid bands at the top of the right panel indicate the range of initial guesses for the two parameters in each fit.