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Doubly robust estimation

As explained in Causal Inference for Data Science

A doubly robust estimator is a causal parameter estimator that combines two estimators and can remain consistent when at least one underlying model is correctly specified.

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

How Causal Inference for Data Science covers it

How deep it goes
Explains AIPW as the primary doubly robust method, combining T-learner and IPW rather than surveying every DR technique.
Examples
Uses binary treatment, outcome, confounder, propensity-score, and available-data examples to motivate AIPW.
What it assumes
Assumes familiarity with adjustment formulas, T-learners, IPW, propensity scores, and the no-unobserved-confounders assumption.
What you can do after
Apply AIPW through the DoubleML library in R or Python to combine causal estimators.
How it connects
Connects causal adjustment to T-learners, propensity scores, inverse probability weighting, machine learning, and the average treatment effect.

Related concepts

This explainer was generated by Manning's knowledge graph from the text of Causal Inference for Data Science. The section links point to the parts of the book it draws on.