A previous study showed that incentivizing students to correct mistakes on unit exam problems within an upper-division quantum mechanics course improved students' problem-solving efforts on those same problems in a final exam environment, relative to a comparison group of students who were not incentivized. We attempt to replicate the quantitative portion of this study within a first-semester upper-division electromagnetism course, specifically examining students' invoking correct concepts and applying those concepts correctly. A statistical comparison of students who accepted the offer to rework unit exam problems for partial credit, versus students who declined the offer, demonstrates a better improvement for students who chose to rework relative to students who declined. As the results suggested that unit exam performance might provide a covariate within the comparison of choice to rework between groups, the results were analyzed using ANCOVA; to understand the effect size, a pre-post normalized gain comparison was also made; statistical results were consistent across both measurements.  Results additionally appear to show that incentivization works more specifically for invoking correct concepts on a primarily conceptual problem, and more specifically for applying concepts correctly on a primarily algorithmic problem. Future plans include a more complete analytical framework using think-aloud protocol interviews for students from the sample, as well as more statistical detail to determine the interaction between unit exam score and choice to rework problems.