Estimator	Formula	Comment
Non parametric (NP) Regression	${\hat{T}}_{N P} = \sum_{i \in s} y_{i} + \sum_{j \in r} \hat{h} (x_{j})$
Nonparametric (NPT) regression, twiced	${\hat{T}}_{N P T} = \sum_{i \in s} \frac{y_{i} - \hat{h} (x_{i})}{π_{i}} + \sum_{j \in U} \hat{h} (x_{j})$	$π_{i} =$ Inclusion probabilities
Multiplicative (MBC) Bias Corrected	${\hat{T}}_{M B C} = \sum_{i \in s} \frac{y_{i} - \hat{h} (x_{i})}{π_{i}} + \sum_{j \in U} \hat{h} (x_{j})$	$π_{i} =$ Inclusion probabilities