Informal learning institutions, such as museums, science centers, and community-based organizations, play a critical role in providing opportunities for students to engage in science, technology, engineering, and mathematics (STEM) activities during out-of-school time hours. In recent years, thousands of studies, evaluations, and conference proceedings have been published measuring the impact that these programs have had on their participants. However, because studies of informal science education (ISE) programs vary considerably in how they are designed and in the quality of their designs, it