Record reviews and historical studies: Studies using existing public surveys, questionnaires and interviews as a base to develop an interview instrument which is first pre-tested on a small group of people from the subject population to identify and eliminate any biases or ambiguities in the way the questions are stated.
Epidemiologic Studies: Studies in which the investigator attempts to identify risk factors for particular diseases, conditions, or behaviors, or risks that result from particular causes, such as the environment or industrial agents.
Controlled clinical trials: Prospective studies designed to assess the safety and efficacy of new drugs, devices, treatments or preventive measures in humans by comparing two or more interventions or regimens.
Each phase of a clinical trial has a different purpose.
Phase III trials: The study drug or treatment is given to large groups of people (1,000-3,000) to confirm its effectiveness, monitor side effects, compare it to commonly used treatments, and collect information that will allow the drug or treatment to be used safely.