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Augmented Inverse Probability Weighting (AIPW) #30

Merged
merged 5 commits into from
Feb 2, 2022
Merged

Augmented Inverse Probability Weighting (AIPW) #30

merged 5 commits into from
Feb 2, 2022

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ehudkr
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@ehudkr ehudkr commented Feb 2, 2022

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:

  • K&S present a version that adds IP-weighed residuals of the outcome and the factual-outcome prediction (attributed to Cassel, Särndal and Wretman).
  • G&Q (citing Robins, Rotnitzky, and Zhao (1994)) additionally weigh the factual-outcome prediction with overlap-weights (i.e. the propensity of the opposite treatment group), and then calculate the residuals and IP-weigh it.
    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.

The two methods only differ by a bit and are both referred to as "AIPW",
so they were consolidated to a single class
(with the IP-weighted-residual-correction being the default one, as it
is slightly more general [applies to multiple treatments] than the
Glynn and Quinn version.
1. Add masked-weight-matrix which is a method from Bang and Robins 2005
   [e(∆, V; β , φ1, φ2)]
2. Add signed-weight-vector, which is from the erratum for Bang and
   Robins (2008): https://doi.org/10.1111/j.1541-0420.2008.01025.x
@ehudkr ehudkr merged commit 9af66b1 into master Feb 2, 2022
@ehudkr ehudkr deleted the aipw branch February 2, 2022 18:10
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