Absence of conflict of interest

The PCER Consortium (2008) study summarized in this intervention report had numerous contributors, including staff of Mathematica Policy Research. Because the principal investigator for the WWC Early Childhood Education review is also a Mathematica staff member, the study was rated by Chesapeake Research Associates, which also prepared the intervention report. The report was then reviewed by the principal investigator, a WWC Quality Assurance reviewer, and an external peer reviewer.