What is propensity score analysis? Propensity score analysis is a collection of methods for estimating the effects of treatments/policies/conditions that removes selection bias due to observed confounders using the propensity score. Commonly-used ways to use the propensity score include weighting, matching, and stratification. Studies using propensity score analysis are quasi-experimental studies, so they provide evidence of a causal effect that is stronger than correlational studies but weaker than experimental studies.
What is a quasi-experimental study? A quasi-experimental study is an evaluation of the effect of a treatment where there is no random assignment to conditions, but there is careful control of selection bias. The difference between quasi-experimental studies and correlational studies is that the former demonstrates baseline equivalence between treatment and control groups with respect to a set of covariates. In propensity score analysis, baseline equivalence is known as covariate balance. What is adequate covariate balance? Definitions vary across fields, but in educational research, baseline equivalence is defined in the Standards of the What Works Clearinghouse of the US Department of Education, as showing that the difference between the treatment and control groups with respect to pre-treatment covariates is either less than 0.05 standard deviations, or between 0.05 and 0.25 standard deviations if the covariates are included in the outcome model. This website aims to facilitate the use of the book Practical Propensity Score Methods Using R, by Dr. Walter Leite, Ph.D., Professor of Research and Evaluation Methodology at University of Florida. Because the book utilizes the R software, new packages and improvements of existing packages for propensity score analysis are published frequently. This website presents updates of the code from the book, as well as related publications by Dr. Leite's team. The book citation in APA format is: Leite, W. L. (2017). Practical propensity score methods using R. Thousand Oaks, CA: Sage Publishing. You can find several videos in the YouTube Channel of the book. The publisher offers free access to chapters 1 and 5, which can be downloaded here. |
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