This discussion will focus mainly on issues pointed out by Dr. Lilly Yue in a paper published in Journal of Biopharmaceutical Statistics (2007, Volume 17: 1-13). Here is the abstract of the paper: “Propensity score analysis is a versatile statistical method used mainly in observational studies for improving treatment comparison by adjusting for up to a relatively large number of potentially confounding covariates. Recently, there has been an increased interest in applying this method to nonrandomized medical device clinical studies. In the application of the methodology, some statistical and regulatory issues arise in both study design and analysis of study results, such as the need for pre-specifying clinically relevant covariates to be measured, appropriate patient populations, and the essential elements of statistical analysis, planning sample size in the context of propensity score m