We ask questions of students in order to probe their understanding. We design our questions in such a way that we can assess a student's progress towards an accurate worldview. However, there is a consensus that a performance gap exists in many physics assessments, where male students outperform their female peers. While early work in this area considered the overall performance gap on testing instruments, in recent years the focus has shifted to item-level gaps. If the reason(s) that performance gaps arise in questions can be identified, then assessment can be designed to reduce or eliminate gender-based biases.