Abstract
The modern medicine relies on evidence from different types of scientific studies. Even though the results of randomized controlled trials are considered as a gold standard for clinical decision-making, observational studies, if well conducted and critically interpreted, provide useful information for the clinical practice.
Observational studies are plaqued with methodological challenges, in particular the presence of bias, that can affect the results of the studies and decrease their validity. This article explains basic methodological concepts that a physician should get aquainted with in order to be able to interpret the results of observational studies.