Optimally and randomly sampled clusters with ages of 1–4 Myr. The colour indicates the metallicity of the cluster, and the marker the age. Top left: mass of the most massive star in the cluster, m_max, against the stellar mass of the cluster, M_cl, for optimally sampled clusters. Top right: same as the top left but for randomly sampled clusters. Bottom left: ratio of the cluster’s Hα luminosity and M_cl against M_cl for optimally sampled clusters. Bottom right: same as the bottom left but for randomly sampled clusters.