Identifiability of causal effect for a simple causal model

Counterfactual model is put forward to discuss the causal inference in the directed acyclic graph and its corresponding identifiability is thus studied with the ancillary information based on conditional independence. It is shown that the assumption of ignorability can be expanded to the assumption of replaceability, under which the causal effects are identifiable.Mathematics, AppliedMathematicsSCI(E)EI1ARTICLE3335-3414