Figure 1.

Epidemiologic methods to estimate average causal effects. The black and white dashed areas indicate the subgroup of the population with disease; the dark gray areas indicate exposed/treated subjects; and the dotted gray area indicates that the exposure is present in the population before manipulation. In an observational study, average causal effects are estimable under the assumptions of exchangeability, consistency, positivity, and correct model specification. In a simulation study, causal effects are estimable under the assumptions of ergodicity and correct model specification.