1Cademy - Game 1 of the Book of Why<br>$X \rightarrow A \rightarrow Y$ <br> $\searrow B$

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Back-Door Criterion

Concept

Game 1 of the Book of Why $X \rightarrow A \rightarrow Y$ $\searrow B$

This diagram has no confounders. B is associated with X because it is in the X->A->Y chain (X->A->B) and it is associated with Y because of the open path of B<-A->Y without having to go through X (where X=0). It also is not a causal path in X->A->Y so it passes the classical epidemilogical definition of a confounder. However, B cannot be a confounder because X is not being impacted by B.