A Parametric Bootstrap Solution to Two-way MANOVA without Interaction under Heteroscedasticity: Fixed and Mixed Models

In this article, we propose a parametric bootstrap (PB) test for heteroscedastic two-way multivariate analysis of variance without Interaction. For the problem of testing equal main effects of factors, we obtain a PB approach and compare it with existing modified Brown-Forsythe (MBF) test and approximate Hotelling T-2 (AHT) test by an extensive simulation study. The PB test is a symmetric function in samples, and does not depend on the chosen weights used to define the parameters uniquely. Simulation results indicate that the PB test performs satisfactorily for various cell sizes and parameter configurations when the homogeneity assumption is seriously violated, and tends to outperform the AHT test for moderate or larger samples in terms of power and controlling size. The MBF test, the AHT test, and the PB test have similar robustness to violations of underlying assumptions. It is also noted that the same PB test can be used to test the significance of random effect vector in a two-way multivariate mixed effects model with unequal cell covariance matrices.