Comparing learning outcomes of two collaborative activities on random genetic drift in an upper-division genetics course

Background: Random genetic drift is a difficult concept for biology undergraduates to understand. Active learning activities in a collaborative setting have the potential to improve student learning outcomes compared to traditional lectures alone and have been shown to help foster success for underrepresented students. However, few activities in this content area have been evaluated for effectiveness in improving student outcomes using peer-reviewed instruments backed by evidence of their validity and reliability. Our aim in this study was to use the Genetic Drift Instrument (GeDI) to evaluate and compare student learning gains in an upper division genetics course in which two different genetic drift activities, a faculty-developed collaborative exercise and a commercially published lab tutorial, were administered in an active-learning classroom with students working in small groups. Methods: The GeDI was administered in both pre- and post-testing in two semesters (n = 95 and 98 students), with the semesters differing in which activity was assigned. Instrument dimensionality, person and item fit, and reliability were evaluated using Rasch analysis. Hierarchical Linear Models (HLMs) with two-way interactions were fitted to assess whether being in a certain Intervention Type, Race/ethnicity, Gender, or First Generation Status affected learning gains. HLMs with three-way interactions were used to assess whether the activities benefited students of all backgrounds equivalently. Results: We found that the GeDI demonstrated unidimensionality, with high item reliability and relatively low person reliability, consistent with previous studies. Both the faculty-developed activity and the commercially available lab tutorial were associated with significant learning gains on genetic drift concepts. Students in the SimBio group had higher learning gains but the difference in effect size was small. No significant differences in learning gains were found between students from different demographic groups, and both activities appeared to benefit students of different backgrounds equivalently. Conclusions: The GeDI instrument could be improved by adding items that more consistently differentiate students of different ability levels, especially at high ability levels. The greater impact on learning gains in the SimBio group while statistically significant does not translate into actual meaningful differences in student understanding. While students of different background variables in the sample have equivalent learning gains and are benefitted equivalently by the different interventions, our interventions did not ameliorate inequities in genetic drift understanding as measured by the GeDI that were uncovered in pre-testing. © The Author(s) 2024.