Editing Analysis of covariance (section)

===Test the homogeneity of regression slopes assumption===
To see if the CV significantly interacts with the categorical IV, run an ANCOVA model including both the IV and the CVxIV interaction term. 
If the CVxIV interaction is significant, ANCOVA should not be performed. Instead, Green & Salkind<ref name="Green">Green, S. B., & Salkind, N. J. (2011). ''Using SPSS for Windows and Macintosh: Analyzing and Understanding Data'' (6th ed.). Upper Saddle River, NJ: Prentice Hall.</ref> suggest assessing group differences on the DV at particular levels of the CV. Also consider using a [[Moderation (statistics)|moderated regression analysis]], treating the CV and its interaction as another IV. Alternatively, one could use [[Mediation (statistics)|mediation analyses]] to determine if the CV accounts for the IV's effect on the DV{{Citation needed|date=December 2022}}.