A Test for Homogeneity of Regression Without Homogeneity of Variance

A likelihood ratio test procedure is described for testing for homogeneity of regression coefficients and population means across treatment groups without assuming homogeneous error variances. Maximum likelihood estimation equations are obtained assuming the criterion scores to be normally distributed, and a method for their solution is described. Examples of situation for which the procedure is appropriate are given, and extensions of the procedure are discussed. The procedure has been used on hypothetical and real data.