Doubly robust estimation improves causal-effect estimates by combining two estimators. If either underlying estimator is unbiased, the combined estimator remains unbiased, providing a safety net when one model is misspecified. It is intended for situations where accuracy and precision matter, such as healthcare or finance. section 8.3 section 8.0
Combining outcome and treatment models
Suppose T is a binary treatment, Y is an outcome, and C contains the confounders. A T-learner estimates expected outcomes under treatment and control, while inverse probability weighting (IPW) estimates propensity scores: the probability of treatment given C. Augmented inverse probability weighting (AIPW) combines these two approaches into a doubly robust estimator of the average treatment effect. The setup assumes no unobserved confounders. section 8.3 section 8.3
Table 8.4 Available data with propensity scores calculated
|
Y
|
T
|
C
1
|
…
|
Cp
|
|---|---|---|---|---|
|
y
1
|
t
1
|
c
1
1
|
…
|
c
1
p
|
|
…
|
…
|
…
|
…
|
…
|
|
y
n
|
t
n
|
c
n
1
|
…
|
c
n
p
|
Inspect the available outcome, treatment, confounder, and propensity-score data used to construct the estimator. section 8.3
