Museums frequently default to simple attendance measures to define success, measures that fall well short of the mission impact these institutions seek to have. Mixed methods studies can integrate quantitative and qualitative findings to paint a robust picture of the impact a museum's educational programming is capable of having, although this design represents significant challenges to staff time and resources and existing instrumentation rarely matches mission precisely. The Morton Arboretum in Lisle, IL used such a design to evaluate its Natural Areas Conservation Training program and its impact with participants, modifying an existing instrument to align with that program's intended outcomes. Results of the study are presented here, as well as insight into the challenges and benefits of modifying existing instrumentation to fit the assessment of a museum's unique mission.