On the Relationship between Bayesian Networks and Probabilistic Structural Causal Models
Authors: Peter J. F. Lucas, Eleonora Zullo, Fabio Stella
Organizations: ICIS, Radboud University, Nijmegen, the Netherlands · Dipartimento di Informatica, Sistemistica e comunicazion University of Milano-Bicocca, Milan, Italy
In this paper, the relationship between probabilistic graphical models, in particular Bayesian networks, and causal diagrams, also called structural causal models, is studied. Structural causal models are deterministic models, based on structural equations or functions, that can be provided with uncertainty by adding independent, unobserved random variables to the models, equipped with probability distributions. One question that arises is whether a Bayesian network that has obtained from expert knowledge or learnt from data can be mapped to a probabilistic structural causal model, and whether or not this has consequences for the network structure and probability distribution. We show that linear algebra and linear programming offer key methods for the transformation, and examine properties for the existence and uniqueness of solutions based on dimensions of the probabilistic structural model. Finally, we examine in what way the semantics of the models is affected by this transformation. Keywords: Causality, probabilistic structural causal models, Bayesian networks, linear algebra, experimental software.
Figures & tables
Figure 1: Two different Bayesian network representations of the same distribution; the top one a regular Bayesian network, whereas the one at the bottom is a Bayesian network representation of a probabilistic structured causal model; (a): priors; (b) posteriors.
Figure 2: Two different Bayesian network representations with two conditional distributions and more values for R , before and after entering an intervention T ; (a): priors; (b): posteriors.
Figure 3: Two different Bayesian network representations of the same distribution with one extra arc from T to R with (a): priors; (b) posteriors.