Clinical trials are studies designed to test the safety and efficacy of new clinical interventions such as drugs or medical devices. Clinical trials differ from other aspects of medical research for three main reasons:
Statistical methodology: Clinical trials have strict design requirements to avoid the introduction of bias in evaluating a new intervention. Clinical trial design is a specialized subset of biostatistics and involves knowledge of design of experiments, power and sample size calculations, and various modeling techniques to control for confounding factors.
Regulation: Clinical trials are used by many regulatory agencies to determine whether or not a drug is safe for use in patient care. Because of the importance of clinical trials in licensing and regulating new drugs and medical devices, clinical trials are subject to strict regulatory requirements regarding recordkeeping and data storage.
Goals of research: Clinical trials are primarily concerned with safety and efficacy. Initial trials may simply investigate whether or not the drug is safe for use in humans, by using relatively healthy subjects. Subsequent trials look for efficacy - that the new drug gives results that are at least as good as the current gold standard during a clinical trial. Drug effectiveness - the ability of the drug to successfully treat illness in actual clinical practice - is not usually assessed in a clinical trial, which is focused strictly on the experimental design that compares the new intervention to an existing intervention.
Clinical trials questions should be tagged using this tag; the epidemiology tag should be used for other health-related research that are not clinical trials.