Treatments can have continuous intensity but in the standard potential outcomes framework they are assumed to be binary. The two most commonly used measures are the average treatment effect (ATE) and the average treatment effect on the treated (ATT): \begin{align} ATE &= E[y_1 - y_0] \newline ATT &= E[y_1 - y_0|D = 1] \end{align} where the dummy $D$ denotes treatment status ($1 =$ treated, $0$ otherwise), whilst $y_1$ and $y_0$ denoted the potential outcomes in the two states. ATE is the expected treatment effect on a randomly extracted unit from the population. ATT is the expected treatment effect on a randomly extracted unit from the sub-population that has been exposed to the treatment.