levels of evidence

Pronunciation: (LEH-vulz ... EH-vih-dents)

A ranking system used to describe the strength of the results measured in a clinical trial or research study. The design of the study (such as a case report for an individual patient or a randomized double-blinded controlled clinical trial) and the endpoints measured (such as survival or quality of life) affect the strength of the evidence.

Source: NCI Dictionary of Cancer Terms