Editing Analysis of covariance (section)

===Assumption 5: homogeneity of regression slopes===
The slopes of the different regression lines should be equivalent, i.e., regression lines should be parallel among groups.

The fifth issue, concerning the homogeneity of different treatment regression slopes is particularly important in evaluating the appropriateness of ANCOVA model. Also note that we only need the error terms to be normally distributed. In fact both the independent variable and the concomitant variables will not be normally distributed in most cases.