Stochastic nature of FASTAR semi-resolved predictions. In the left panel, each row shows five random semi-resolved SSP models (in gray) resulting from different stochastic samplings of the IMF. The corresponding IMF realizations are shown in the right panels (also in gray), along with the assumed IMF (red) and the mean stellar mass of the population. For reference, the standard fully sampled SSP prediction is included in red in the left panels (scaled to arbitrary units for comparison). All realizations correspond to a 10 Gyr, solar-metallicity population. From top to bottom, the number of stars increases from 10 to 1 000 000.