Generalized and oxdinary least squakes with estimated and unequal variances

Abstract

An assumption which is often violated in the application of experimental designs is equality of variances. There are several methods available for estimating the unequal variances. This paper covers incorporating different estimators of the variances with the ordinary least squares and generalized least squares. A Monte Carlo study provides more insight into the behavior of these procedures. For some small sample sizes, the incorporations with the ordinary least squares perform satisfactorily, but with the generalized least squares they do not.

Keywords:

• linear models
• heteroscedasticity