Causal graphs illustrating the effect of interventions.

<p><b>A</b>: Graph showing a case where the statistical dependence between and is (partly) due to a causal interaction from to . <b>B</b>: Graph showing a case where the statistical dependence between and is induced solely by the confounding variable . <b>C</b>: Graph corresponding to the intervention in the causal graph shown in <b>A</b>. <b>D</b>: Graph corresponding to the intervention in the causal graph shown in <b>B</b>.