A cornerstone of EBM is the hierarchical system of classifying evidence known as the levels of evidence. Levels of evidence (LOE) are used to describe the strength of the results measured in a clinical trial or research study. Evidence is ranked based on its reliability. LOE models review data based on the elements of study design, quality, and consistency of evidence.
Start at the top of the pyramid for the most reliable evidence, keeping in mind that research may not yet exist or may not be feasible for some questions.