Here are definitions for the three study types used in class: Clinical Study; Controlled Clinical Trial and Randomized Controlled Trial.
Source: National Institute of Health/ National Library of Medicine Publication Characteristics (Publication Types) with Scope Notes - 2017 MeSH Edition: https://www.nlm.nih.gov/mesh/pubtypes.html
A work that reports on the results of a research study to evaluate interventions or exposures on biomedical or health-related outcomes. The two main types of clinical studies are interventional studies (clinical trials) and observational studies. While most clinical studies concern humans, this publication type may be used for clinical veterinary articles meeting the requisites for humans.
Controlled Clinical Trial:
A work that reports on a clinical trial involving one or more test treatments, at least one control treatment, specified outcome measures for evaluating the studied intervention, and a bias-free method for assigning patients to the test treatment. The treatment may be drugs, devices, or procedures studied for diagnostic, therapeutic, or prophylactic effectiveness. Control measures include placebos, active medicine, no-treatment, dosage forms and regimens, historical comparisons, etc.
Randomized Controlled Trial:
A work that reports on a clinical trial that involves at least one test treatment and one control treatment, concurrent enrollment and follow-up of the test- and control-treated groups, and in which the treatments to be administered are selected by a random process, such as the use of a random numbers table, to assign patients to test or control treatments.