A way of choosing the people for a study by letting them set themselves apart from a larger group in some way; for example, by responding to a questionnaire or by going to a program.

When eligibility for membership in sample or a study group is based on an individual characteristic, the sampling procedure is usually termed “self-selection.” For example, participants in a study comparing smokers to non-smokers would be assigned to one group or the other depending on their own decision to smoke or not. Self-selection generally precludes being able to control for the effect of other variables and observed group differences may not be due to the characteristic that determined selection.

Freedom for patients to examine and select medicines without assistance.