To determine which of two candidate models (model 1 and model 2, say), describes the data better and to evaluate the degree of confidence in the preference, the joint posterior probability 𝑃({𝒃 𝑙 }, ℋ|𝑨) (where ℋ is the model class being used, 𝑨 denotes the adjacency matrix, and 𝒃 𝑙 is the partition of blocks in level 𝑙) of each model can be compared via their ratio Λ 1 (8):