In this video from Physics by Inquiry, a researcher explains how they have used a posttest to assess the ability of high school teachers in a professional development program to apply what they have learned to new situations. The majority can correctly predict the behavior of light in a new scenario after working through an inquiry-based module. They in fact perform better than physics faculty and graduate students do on a pretest, indicating that that the study of advanced material does not necessarily deepen understanding of basic concepts.