Augmented Inverse Probability Weighting (AIPW) #30
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Completing PR #28.
Glynn and Quinn (2010) present a version of AIPW that is different from the one described in Kang and Schafer (2007, section 3.1).
The two methods are comparable, but slightly differ from one another:
This might be beneficial as it will rely less on outcome-prediction of extreme-propensity data points - those lacking covariate overlap and more prone to model extrapolation. However, since it also rely on opposite-group, it is limited to a binary-treatment setting.
Since both versions are frequently referred to as "AIPW", and since code overlap a lot, it is better to consolidate them to a single AIPW class.
Additionally, following up on the changes in #28,
It appears Bang and Robins 2005 has a 2008 errata describing the IP-feature as needing a negation to the control group (matching with Hernán and Robins book Fine Point 13.2, and aligning with the ATE-targeted version of TMLE).
Additionally, a masked-IPW matrix (described as
e(∆, V; β , φ1, φ2)
in B&R) is also added.These two were previously commented out, as they seem to have bigger variance (less-efficient) than the other methods on some simple simulated datasets, but they are theoretically justifiable, so they are added anyway.