Example of the χ² distribution for determination of the stellar mass, the age and the metallicity of region 25. The confidence limits around the best-fit ages (3σ), indicated by the vertical bands, are obtained from the given χ² distribution following Avni (1976). We note that all the models with an age of less than 6 Myr for this region are rejected due to upper limit violations, resulting in the unusual single-sided χ² distribution above (the other side could be represented by a vertical line if we assign artificially infinite χ² to rejected models). Similar χ² distributions for all the other regions are provided in Appendix A.