What do we do when we go to actually estimate quantities such as 𝔼 𝑋 [ 𝔼[𝑌 | 𝑇 = 1, 𝑋] − 𝔼[𝑌 | 𝑇 = 0, 𝑋] ] ? We will often use a model (e.g. linear regression or some more fancy predictor from machine learning) in place of the conditional expectations 𝔼[𝑌 | 𝑇 = 𝑡, 𝑋 = 𝑥] . We will refer to estimators that use models like this as model-assisted estimators. Now that we’ve gotten some of this terminology out of the way, we can proceed to an example of estimating the ATE