Randomized controlled trials description

Quality of evidence I, evidence from >1 properly randomized, controlled trial II, evidence from <1 well-designed clinical trial, without randomization from cohort or case-controlled analytic studies (preferably from >1 center) or from multiple time-series III, evidence from opinions of respected authorities, based on clinical experience, descriptive studies, or reports of expert committees. 

Dobbins, M., Robeson, R, Ciliska, D., Hanna, S., Cameron, R., O Mara, L., DeCorby, K. and Mercer, S. (2009). A description of a knowledge broker role implemented as part of a randomized controlled trial evaluating three knowledge translation strategies. Implementation Science, 4, pp. 1-9. 

---