Impact of Outcome Model Misspecification on Regression and Doubly-Robust Inverse Probability Weighting to Estimate Causal Effect
Bibliographic record
Abstract
Estimating treatment effects with observational data requires adjustment for confounding at the analysis stage. This is typically done by including the measured confounders along with the treatment covariate into a regression model for the outcome. Alternatively, it is also possible to adjust for confounding by taking into account the propensity of an individual to receive treatment, with inverse probability weighting (IPW). In the class of IPW estimators, the so-called doubly-robust estimator also requires the specification of the outcome regression model, in addition to the propensity model. The aim of this paper is to investigate the impact of misspecification of the outcome model on the performances of the usual regression and doubly-robust IPW estimators for estimating treatment effects. We examine the performances of the estimators across the parameter space for different scenarios of model misspecification using large-sample theory. We find that for small-to-moderate sample sizes, the regression estimator compares favorably to the IPW doubly-robust estimator. Finally we argue, both conceptually and on the basis of our results, that treatment-confounder interactions should be included in the outcome regression model.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.145 | 0.423 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.002 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.003 |
| Scholarly communication | 0.002 | 0.004 |
| Open science | 0.003 | 0.004 |
| Research integrity | 0.002 | 0.003 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".