Group comparisons offer students opportunities to reason about many fundamental statistical concepts like center, variation, or distribution. When doing such activities using large, real datasets, technology becomes an essential tool for exploring the data. With its large variety of features and its user-friendly handling, TinkerPlots™--as a software for learners and teachers--can facilitate the process of comparing distributions. In this article we focus on eight preservice teachers´ reasoning when comparing groups with TinkerPlots. We present ideas on the design of a course to develop statistical reasoning with TinkerPlots, present a framework to rate learners´ performance when comparing groups with TinkerPlots, and present results of a laboratory study about preservice teachers´ reasoning when comparing groups with TinkerPlots. Findings suggest that the TinkerPlots tool and design of the course supported these preservice teachers' reasoning and that more learning opportunities are needed to increase their group comparison elements' repertoire and interpretation in context.