Guide to understanding observational studies that use real-world data

This introductory article is part of a series about the analyses used for studies using routine health data. The contents of this article provide a brief background on real-world data (RWD) itself and observational studies; both the advantages and the disadvantages of using RWD for observational studies, and how to critically appraise these studies. Other articles in this series will then discuss specific analyses applied to RWD, such as interrupted time series, difference-in-differences and the role of RWD in randomised-controlled trials (RCTs).