Analysis of Covariance

Abstract

Experiments which involve variables (covariates) that affect the response but that are not of direct interest nor can be controlled during the design of the experiment can be analyzed by the technique of analysis of covariance. This technique adjusts the treatment parameter estimates for the estimated values of the covariates. This chapter describes standard analysis of covariance models. Treatment parameter estimates are obtained via least squares, and analysis of covariance tests and confidence interval methods for the comparison of treatment effects are also developed. The concepts introduced in this chapter are illustrated through examples and use of SAS and R software.