Measures that accurately capture the phenomenon are critical to research and practice in group work. The vast majority of group-related measures were developed using the reflective measurement model rooted in classical test theory (CTT). Depending on the construct definition and the measure's purpose, the reflective model may not always be the most appropriate. Two other models, Rasch and formative, present viable alternatives. In this article, we describe reflective, formative, and Rasch models using the examples of group conflict and group facilitation skills. We then provide practical guidelines for construct definition and item writing as they relate to each measurement model.