Fig. 1
From: Steady state trials: another valid substitution of counterfactual ideal to measure causal effects
Counterfactual model. We establish a hypothetical person in the counterfactual world in order to compare the outcome of the exposed person with the outcome of the unexposed person. After the exposure, both the conditions of the exposed person and the unexposed person are observed at the same time. As the only difference between the two settings is the exposure, it is possible to measure the effect of the exposure