Top row, left panel: boxplots of the computed d² statistics for clusters of n = 300 stars generated by an isochrone at 150 Myr. The overshooting parameter β is 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 dashed blue line marks the significance at the 5% level. Centre: same as in the left panel, but for an age of 1 Gyr. Right panel: same as in the left panel, but for an age of 7 Gyr. Middle row: same as in the top row, but generating synthetic data from an isochrone with modified ¹⁴N(p, γ)¹⁵O reaction rate. Bottom row: same as in the top row, but generating synthetic data from an isochrone with a modified microscopic diffusion efficiency.