Most free-choice science learning institutions, in particular science centers, zoos, aquariums, and natural history museums, define themselves as educational institutions. However, to what extent, and for which visitors, do these free-choice learning settings accomplish their educational mission? Answering this question has proven challenging, in large part because of the inherent variability of visitors to such settings. We hypothesize that the challenges of measuring free-choice science learning might be diminished if it were possible to pool populations during analysis in ways that reduced