Combining Double Sampling and Bounds to Address Non-Ignorable Missing Outcomes in Randomized Experiments
24 Pages Posted: 5 Aug 2013 Last revised: 27 Jun 2016
Date Written: June 26, 2016
Missing outcome data plague many randomized experiments. Common solutions rely on ignorability assumptions that may not be credible in all applications. We propose a method for confronting missing outcome data that makes fairly weak assumptions but can still yield informative bounds on the average treatment effect. Our approach is based on a combination of the double sampling design and non-parametric worst-case bounds. We derive a worst-case bounds estimator under double sampling and provide analytic expressions for variance estimators and confidence intervals. We also propose a method for covariate adjustment using post-stratification and a sensitivity analysis for non-ignorable missingness. Finally, we illustrate the utility of our approach using Monte Carlo simulations and a placebo-controlled randomized field experiment on the effects of persuasion on social attitudes with survey-based outcome measures.
Keywords: causal inference, experiments, missing data, bounds, ignorability
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