Date of this Version
Regressions can be weighted by propensity scores in order to reduce bias. However, weighting is likely to increase random error in the estimates, and to bias the estimated standard errors downward, even when selection mechanisms are well understood. Moreover, in some cases, weighting will increase the bias in estimated causal parameters. If investigators have a good causal model, it seems better just to fit the model without weights. If the causal model is improperly specified, there can be significant problems in retrieving the situation by weighting, although weighting may help under some circumstances.
causation, selection, models, experiments, observational studies, regression, propensity scores
Freedman, D. A., & Berk, R. A. (2008). Weighting Regressions by Propensity Scores. Evaluation Review, 32 (4), 392-409. http://dx.doi.org/10.1177/0193841X08317586
Date Posted: 27 November 2017
This document has been peer reviewed.