All clinical trials have guidelines about who can participate in a study. Guidelines are based on such factors as age, type of disease, medical history, and current medical condition. Some research studies seek volunteers with illnesses or conditions to be studied, while other trials need healthy volunteers.
Factors that allow you to participate in a study are called "inclusion criteria". Factors that keep you from participating are called "exclusion criteria". The criteria are not used to reject people for any personal reason, but rather are used to identify appropriate participants and keep them safe. The criteria also help researchers ensure they will be able to answer the questions they plan to study. clinical trial (also clinical research) is a research study in human volunteers to answer specific health questions. Carefully conducted clinical trials are the fastest and safest ways to find treatments that work in people and ways to improve health. Interventional trials determine whether experimental treatments or new ways of using known therapies are safe and effective under controlled environments. Observational trials address health issues in large
groups of people of populations in natural settings.