Graphical model summarising the mass modelling framework that we present in Sect. 3.3. The symbols are also described in that section; in summary, the symbol μ represents mass, κ is the bias term, δ is the scatter term and σ is the measurement error term (all in log space), and the C and X subscripts denote whether the quantity refers to that from the hydrostatic or caustic method. The refers to an observed quantity. 𝒩 refers to a normal distribution, and ‘∼’ denotes ‘is distributed as’.