Predictive and explanatory models might miss informative features in educational data

We encounter variables with little variation often in educational data mining (EDM) and discipline-based education research (DBER) due to the demographics of higher education and the questions we ask. Yet, little work has examined how to analyze such data. Therefore, we conducted a simulation study using logistic regression, penalized regression, and random forest. We systematically varied the fraction of positive outcomes, feature imbalances, and odds ratios. We find the algorithms treat features with the same odds ratios differently based on the features' imbalance and the outcome imbalance. While none of the algorithms fully solved the problem, penalized approaches such as Firth and Log-F reduced the scale of the problem. Our results suggest that EDM and DBER studies might contain false negatives when determining which variables are related to an outcome. We then apply our findings to a graduate admissions data set and we propose recommendations for researchers working with the kind of imbalanced data common to EDM and DBER studies.