Comparing groups is a fundamental skill preservice teachers are supposed to gain after attending a statistics course at university level. Preferably these activities are embedded in the well-known PPDAC-Cycle and contain the exploration of real and motivating data. Adequate software such as TinkerPlots may support learners when exploring data and carving out differences between distributions of numerical variables. In this article we want to present first results of a study on statistical reasoning of preservice teachers while doing group comparisons with TinkerPlots.