We are grateful to Fred Goldberg, Steve Robinson, Ed Price, Rebecca Kruse, RhettAllain, and Nephi Thompson for their work on PET and PSET; to Kathy Perkins for her guidance on the CLASS analysis; and to the faculty and students who participated in this study. We are thankful for the support of the National Science Foundation Award No. DRL0554616, the American Physical Society, and the Physics Teachers Education Coalition.