On the equality of the ordinary least squares estimators and the best linear unbiased estimators in multivariate growth-curve models

It is well known that there were proved several necessary and sufficient conditions for the ordinary least squares estimators (OLSE) to be the best linear unbiased estimators (BLUE) of the fixed effects in general linear models. The purpose of this article is to verify one of these conditions given by Zyskind [39, 40]: there exists a matrix Q such that X = XQ, where X and are the design matrix and the covariance matrix, respectively. It will be shown the accessibility of this condition in some multivariate growth-curve models, establishing the known result regarding the equality between OLSE and BLUE in this type of linear models