Implementing double-robust estimators of causal effects
Richard Emsley (),
Mark Lunt,
Andrew Pickles and
GraHam Dunn Additional contact information Richard Emsley: Biostatistics, Health Methodology Research Group, The University of Manchester
Mark Lunt: Arthritis Research Campaign Epidemiology Unit, The University of Manchester
Andrew Pickles: Biostatistics, Health Methodology Research Group, The University of Manchester
GraHam Dunn: Biostatistics, Health Methodology Research Group, The University of Manchester
Abstract:
This article describes the implementation of a double-robust estimator for pretest-posttest studies (Lunceford and Davidian, 2004, Statistics in Medicine 23: 2937-2960) and presents a new Stata command (dr) that carries out the procedure. A double-robust estimator gives the analyst two opportunities for obtaining unbiased inference when adjusting for selection effects such as confounding by allowing for different forms of model misspecification; a double-robust estimator also can offer increased efficiency when all the models are correctly specified. We demonstrate the results with a Monte Carlo simulation study, and we show how to implement the double-robust estimator on a single simulated dataset, both manually and by using the dr command. Copyright 2008 by StataCorp LP.