Propensity score model overfitting led to inflated variance of estimated odds ratios

Matching on the Estimated Propensity Score

Propensity score matching estimators (Rosenbaum and Rubin, 1983) are widely used in evaluation research to estimate average treatment effects. In this article, we derive the large sample distribution of propensity score matching estimators. Our derivations take into account that the propensity score is itself estimated in a first step, prior to matching. We prove that first step estimation of t...

Evaluation of the Propensity score methods for estimating marginal odds ratios in case of small sample size

BACKGROUND Propensity score (PS) methods are increasingly used, even when sample sizes are small or treatments are seldom used. However, the relative performance of the two mainly recommended PS methods, namely PS-matching or inverse probability of treatment weighting (IPTW), have not been studied in the context of small sample sizes. METHODS We conducted a series of Monte Carlo simulations t...

Making sense of odds and odds ratios.

Odds and odds ratios are hard for many clinicians to understand. Odds are the probability of an event occurring divided by the probability of the event not occurring. An odds ratio is the odds of the event in one group, for example, those exposed to a drug, divided by the odds in another group not exposed. Odds ratios always exaggerate the true relative risk to some degree. When the probability...

Nber Working Paper Series Matching on the Estimated Propensity Score

We are grateful to Ben Hansen, James Robins, Paul Rosenbaum, Donald Rubin, and participants in seminars at the Banff Center, Brown, Georgetown, Harvard/MIT, Montreal, and UPenn for comments and discussions. Software implementing these methods is available on our websites. The views expressed herein are those of the author(s) and do not necessarily reflect the views of the National Bureau of Eco...

Mischievous Odds Ratios