Top row, left panel: boxplots of the computed d² statistics for clusters of n = 300 stars generated by an isochrone at 1 Gyr. The overshooting parameter β changed by ±0.05 with respect to the reference isochrone. The statistics was computed with respect to the reference isochrone at the same age. The generated stars were constrained to have G < 7 mag. The dashed blue line marks the significance at 5% level. Centre: same as in the left panel, but generating synthetic data from an isochrone with modified ¹⁴N(p, γ)¹⁵O reaction rate. Right panel: same as in the left panel, but generating synthetic data from an isochrone with modified microscopic diffusion efficiency. Bottom row, left panel: same as in the top row, left panel, but for a difference in the colour systems. Centre: same as in the left panel, but generating synthetic data from an isochrone with BH05 boundary condition. Right panel: same as in the left panel, but generating synthetic data from an isochrone with a KS66 boundary condition.