Concentration graph models are an attractive tool to explore the conditional independence structure in a multivariate normal distribution. In applications, in absence of a priori knowledge, it is possible to select the graph underlying a set of data through an appropriate model selection...

In this paper, we propose a way to incorporate multilevel models within graphical models. We introduce three types of nodes for chain graphs to represent (1) individual within clusters, (2) clusters as latent variables and (3) interactive effects. In this way, the chain graph shows both the...