Application of Propensity Score Models and Causal Estimators in Observational Studies under Model Misspecification
This study systematically evaluates the robustness of response surface modeling (RSM), inverse probability weighting (IPW), and augmented inverse probability weighting (AIPW) under various misspecification scenarios of propensity score and outcome models in observational studies. Leveraging multiple methods—including logistic regression, random forests, support vector machines, and linear discriminant analysis—to estimate propensity scores, the authors assess performance through extensive simulations and real-world applications to the ACTG175 and ADNI datasets. Findings indicate that AIPW demonstrates consistent robustness across most settings, benefiting from its double-robustness property; IPW proves highly sensitive to propensity score misspecification, while RSM performs well only when the outcome model is correctly specified. The results underscore that integrating flexible machine learning techniques within a doubly robust framework substantially enhances the reliability of causal effect estimation.