A SIMULATION STUDY ON DUNNETT TEST ROBUSTNESS TO GROUP SIZE AND HETEROSCEDASTICITY IN LINEAR MIXED-EFFECTS MODELS

In linear mixed-effects models, the Dunnett procedure is commonly employed for comparing multiple groups against a control group. While the influence of group number on the Dunnett test’s performance is well-documented, the effects of heteroscedasticity and unequal group sizes remain underexplored. This study investigates the robustness of the Dunnett test within linear mixed-effects models, particularly in the presence of heteroscedasticity, varying group sizes, and different group numbers. Through data simulation, we assessed performance using four key metrics: any-pairwise-power, all-pairwise-power, type I error rate, and false discovery rate. Our findings indicate that the procedure’s performance diminishes significantly when fewer than seven groups are involved, especially when group sizes are small and variances are heterogeneous. Under these circumstances, the type I error rate deviates from the nominal level, despite adequate power estimates being achieved.