Exploring pedagogical content knowledge of physics instructors using the force concept inventory

The Force Concept Inventory (FCI) has been widely used to assess student understanding of introductory mechanics concepts by educators and physics education researchers. Many of the items on the FCI have strong distractor choices corresponding to students' alternate conceptions in mechanics. Instruction is unlikely to be effective if instructors do not explicitly take into account students' initial knowledge state in their instructional design. We discuss research involving the FCI to evaluate the pedagogical content knowledge of instructors of varying teaching experience. For each item on the FCI, instructors were asked to identify the most common incorrect answer choice of introductory physics students. We also discussed the responses individually with some instructors. Then we used the FCI pre-test and post-test data from a large population (~900) of introductory students to assess the pedagogical content knowledge of the physics instructors related to the FCI. While the physics instructors, on average, performance better than random guessing at identifying introductory students' difficulties with FCI content, they did not identify many common difficulties of introductory physics students. Moreover, the ability to correctly identify students' difficulties was not correlated with the teaching experience of instructors.