The terms and conditions of Section 1115 welfare waivers specify several steps designed to reduce the incidence of cases crossing over from control group policies to experimental group policies (or vice versa):
- When a case relocates from one research site to another research site, the case's experimental/ control status is to be preserved.
- When a research case splits into multiple cases remaining in a research site, the original case's experimental/control status is to be preserved for the new cases.
- When an experimental/control case merges with another case in the same research site, the experimental/control status of the head of the new case is to be preserved.
These standards do not address crossover that occurs through administrative errors in the classification of cases' experimental or control status.