Three modifications of the principle of the minque
Nonnegative estimators for the variance components of a linear model are obtained by ignoring the condition for unbiasedness in the principle of the MINQUE. An estimator is derived when the priori weights are proportional to the variance components. The ordinary sample variance is shown to be the nonnegative MINQUE. Efficiencies of the three estimators are examined for some special cases of the model.