en Biostatistics and Epidemiology Biostatistics and Epidemiology Debate Article Debate Article <p><strong>&nbsp;&nbsp;</strong>&nbsp; In the statistical analysis of observational data, propensity score is a technique that attempts to estimate the effect of a treatment (exposure) by accounting for the covariates that predict receiving the treatment (exposure). The aim of this paper is to provide a brief guide for clinicians and researchers who are applying propensity score analysis as a tool for analyzing observational data. We reviewed literature about how, when and why propensity score is used and then we discussed some important practical issues in using propensity score in observational studies. Appling propensity score as a method for analyzing observational studies is very useful but, we should know when and how we can use this method. Moreover, new methods of propensity score analysis such as Bayesian and doubly robust approaches were established in recent years, and these methods could be more useful for researchers in estimating causal effect from observational studies.<br> &nbsp;</p> Propensity score, Observational study, Causal inference 717 720 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-2158-1&slc_lang=en&sid=1 Ameneh Ebrahim Valojerdi ebrahimi.am@tak.iums.ac.ir 200319475328460042279 200319475328460042279 No Endocrine Research Center, Institute of Endocrinology and Metabolism, Iran University of Medical Sciences, Tehran, Iran leila Janani janani.l@iums.ac.ir 200319475328460042280 200319475328460042280 Yes Department of Biostatistics, School of Public Health, Iran University of Medical Sci-ences, Tehran, Iran, & Preventive Medicine and Public Health Research Center, Iran University of medical sciences, Tehran, Iran