Randomization is a research method that helps prevent the results of a clinical trial from being biased. Participants agree to be randomly assigned, that is, assigned by chance, to one group or another in the research study. Randomization is usually done by a computer. Phase IV trials may be done after the new drug, or treatment, is already approved for use by the Food and Drug Administration. These studies continue to test the effects of the drug on different types of people, and to look for long-term side effects.
Clinical trials vary, but each clinical trial follows a set of rules called a protocol .
The protocol explains what will happen during the clinical trial. It describes the purpose of the trial, how it will be carried out, and why each part of the study is necessary. For example, the protocol explains who can join the trial. This may be based on such factors as type of disease, medical history, current condition or past treatment. Participants in a trial may have more tests and health care visits than they would if they were not in the trial.