How strict should my validation rules be?

When planning your validation rules, consider how strictly you will interpret the study guidelines, and create a validation rule only if you will never accept data outside a certain range.

For example, consider an enrollment criterion for age: Subjects must be at least 18 years old. With a strict validation rule for age, a prospective subject who is 17 years old at the screening visit fails screening, even if the subject will be 18 years old by the time of the first visit. This strict validation rule would prevent a site user from enrolling a subject who nearly meets the enrollment criteria, though a site user could rescreen a subject who later becomes eligible.