Research studies come in many different forms. Experts in the field of evidence-based social work practice often rank types of research studies according to their reliability. These rankings often take the form of an an evidence hierarchy. In this page, you will see an evidence hierarchy outlined by Nathan and Gorman (2015).
In A Guide to Treatments that Work, Nathan and Gorman outline a hierarchy of research articles. Articles based on type 1 studies represent the most reliable form of evidence.
Nathan, P.E. & Gorman, J.M. (2007). A guide to treatments that work. Oxford: Oxford University Press.