In a clinical study, eligibility criteria are the requirements that must be met for a person to be included in the study. These requirements help make sure that participants in a trial are like each other in terms of specific factors such as age, disease or stage of disease, general health, and previous treatment. When all participants meet the same eligibility criteria, it is more likely for example that results of the study are caused by the therapy being tested and not by other factors or by chance.
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