[Experimental studies: research designs for the evaluation of interventions in clinical settings].

Experimental studies are used to assess the efficacy and effectiveness of therapeutic (pharmacological or surgical), preventive (such as vaccination or lifestyle changes) or educational interventions (e.g., workshops to improve quality and healthcare). There are different experimental studies but, currently, randomized controlled trial (RCT) is recognized as the type of study that provides the highest level of evidence. When this type of research cannot be carried out, there are quasi-experimental studies, where there may be no randomization or a control group; however, this type of studies has a lower degree of validity. This article describes the way different types of RCT and quasi-experimental studies are performed; their advantages and disadvantages are also explained.