" The Bureau is continuing its early testing efforts to prepare for the decennial. These tests must be well designed to produce useful information about how to implement the 2020 Census. The Bureau has completed the designs of three field tests. GAO was asked to monitor the Bureau's testing for the 2020 Census. This report (1) determines the extent to which the Bureau followed key practices for a sound study plan in designing the earliest 2020 Decennial Census field tests, and (2) identifies what lessons were learned that may help improve future tests. To meet these objectives, GAO first selected 25 key practices for a sound research plan after reviewing its program evaluation literature. GAO then compared Bureau field test design documents for its three initial tests to these practices. GAO also examined where the Bureau had not followed key practices, identified actions needed to address them, and interviewed officials about lessons learned. "