 The intention-to-treat principle is a method used in randomized controlled trials to ensure that all participants are analyzed according to the group they were originally assigned, regardless of whether or not they actually received the intended treatment. This method preserves the benefits of randomization, which cannot be assumed when using other methods of analysis. Per protocol analysis is the opposite of intention-to-treat analysis, it excludes participants who did not receive the intended treatment, thus increasing the risk of bias. Using the wrong method of analysis can lead to a significantly biased assessment of the effectiveness of an intervention. This article was authored by C. Eric McCoy.