Probabilistic graphical model used to fit the mean age/mass and intrinsic age/mass spread. We assume the measured ages/masses (X) are drawn from an underlying true θ distribution that is Gaussian with a mean μ and standard deviation σ. We assume that the true age (mass) distribution is contaminated by stars whose mass is higher than expected. We model these contaminants as also being drawn from another normal distribution with a mean μ_c and spread σ_c which has a fractional contribution ϵ to the total age distribution (hence the main population contributes 1 − ϵ).