Propensity Score Matching - Statpower

IntroductionModeling the CovariatesSubclassificationMatchingBalancing ScoresThe Propensity ScoreMatching MethodsUsing Propensity Scores – A General StrategyAn ExampleMatching and SubclassificationIn previous discussions, we learned about selection bias and, inparticular, the dangers of attempting to control forpost-treatment covariates while assessing causality.Near the end of Chapter 10, Gelman & Hill discuss the methodsof matching and subclassification as aids to causal inference inobservational studies.The basic idea behind the methods is that, if you can identifyrelevant covariates so that ignorability is reasonable, you canassess causality by controlling for the covariates statistically.Such control can take several forms:You can examine conditional distributions, conditionalizedon classifications on the covariate(s).You can match treatment and controls, and comparematched groupsYou can model the covariates along with the treatmentMultilevelPropensity Score Matching