A clinical trial is one of the final stages of a long and careful research process. For example, a scientist first thoroughly studies a potential new drug in the laboratory and then makes sure it is safe and effective on animals. But, even if this new medicine helps sick animals, it may not always be effective for humans. Scientists use clinical trials to make sure that new treatments and procedures work reliably for the humans they were designed to help.
Although there are many definitions of clinical trials, they are generally considered to be biomedical or health-related research studies in human beings that follow a pre-defined protocol. ClinicalTrials.gov includes both interventional and observational types of studies. Interventional studies are those in which the research subjects are assigned by the investigator to a treatment or other intervention, and their outcomes are measured. Observational studies are those in which individuals are observed and their outcomes are measured by the investigators.
