Editing Analysis of covariance (section)

===Follow-up analyses===
If there was a significant [[main effect]], it means that there is a significant difference between the levels of one categorical IV, ignoring all other factors.<ref name="Howell">Howell, D. C. (2009) ''Statistical methods for psychology'' (7th ed.). Belmont: Cengage Wadsworth.</ref> To find exactly which levels are significantly different from one another, one can use the same follow-up tests as for the ANOVA.
If there are two or more IVs, there may be a [[Interaction (statistics)|significant interaction]], which means that the effect of one IV on the DV changes depending on the level of another factor. One can investigate the simple main effects using the same methods as in a [[Factor analysis|factorial ANOVA]].