SBC test of the posteriors for 1000 synthetic test observations. The red histograms in each panel represent the distribution of the rank statistic of the true value within the marginalised posterior for the percentiles 10%, 50%, and 90% and for [M/H]. For a well-calibrated posterior, the rank statistics will have a uniform distribution (dashed black line). The grey band indicates 99% of the variation expected from a uniform histogram. The rank statistic distributions of our posteriors are nearly uniform for all four parameters, and therefore, the model provides unbiased and accurate posteriors.