  The Test of Understanding Graphs in Kinematics (TUG-K) is a multiple choice
test developed by Beichner to assess students' understanding of kinematics
graphs. Many of the items on the TUG-K have strong distractor choices which
correspond to introductory students' common difficulties with kinematics
graphs. Instruction is unlikely to be effective if instructors do not know
these common difficulties and take them into account in their instructional
design. We evaluate the performance of first year physics graduate students at
identifying introductory students' common difficulties related to kinematics
graphs. In particular, for each item on the TUG-K, the graduate students were
asked to identify which incorrect answer choice they thought would be most
commonly selected by introductory physics students if they did not know the
correct answer after instruction in relevant concepts. We used the introductory
student data from Beichner's original paper to assess graduate students'
knowledge of introductory students' difficulties. Furthermore, we selected the
four questions on the TUG-K on which the graduate student performance was the
poorest for a more detailed analysis which included think-aloud interviews. We
present results which can partly account for the poor graduate student
performance on these questions and also inform instruction in professional
development courses.
