1. A general term used to refer to any one of a variety of research activities involving the collection, analysis, or interpretation of data.
2. Synonym for clinical trial.
3. A project involving multiple types of investigations, only one of which is a clinical trial (as in a Coronary Artery Surgery Study since it includes both a clinical trial and an uncontrolled prospective follow-up study).

  Treatment Trial . A trial in which the test treatment consists of a procedure used in the treatment of a specific disease or health condition.

  Controlled Trials . Generally trials in which one group gets the experimental drug. The other group, the control group, is given either a placebo or an approved drug therapy. Participants usually do not know which group they are in.

  Uncontrolled Clinical Trials . A clinical trial that does not involve a control treatment. Any study that does not have a control group consisting of patients treated and followed up over the same time period as those in a treated group.

  Comparative Study . A study comparing two things, such as two different drugs, or two dosages of the same drug.

  Double-Blind Trial, Double-blind clinical study . A study in which none of the participants, including the experimental subjects, examining doctors, attending nurses, or any other research staff, know who is taking the test drug and who is taking a control (or placebo) agent. The purpose of such a research design is to avoid any inadvertent bias of the test results. In all such studies, procedures exist to "break the blind" if circumstances require it.

  Risk Factor Analysis . Any analysis, usually involving regression or subgroup analyses, that is aimed at identifying risk factors for a given disease or condition.