Conventional and approximate degrees of freedom procedures for testing multivariate interaction contrasts in groups by trials repeated measures designs were compared under assumption violation conditions. Procedures were based on either least-squares or robust estimators. Power generally favored test procedures based on robust estimators for non-normal distributions, but was influenced by the degree of departure from non-normality, definition of power, and magnitude of the multivariate effect size.
Lix, Lisa M. and Hinds, Aynslie M.
"Multivariate Contrasts For Repeated Measures Designs Under Assumption Violations,"
Journal of Modern Applied Statistical Methods: Vol. 3
, Article 7.
Available at: http://digitalcommons.wayne.edu/jmasm/vol3/iss2/7