The main effects plot and interaction plots are effective graphical tools. They often convey more information than the numerical values of main effect and interaction effect estimates. For factors A...

The main effects plot and interaction plots are effective graphical tools. They

often convey more information than the numerical values of main effect and

interaction effect estimates. For factors A and B, there are the A-against-B

plot and the B-against-A plot. An A-against-B plot is called synergistic if

ME(B|A+)ME(B|A−) > 0 and antagonistic if ME(B|A+)ME(B|A−)

An antagonistic A-against-B plot suggests that the underlying response

relationship may be more complicated and that, at an intermediate setting

between A+ and A−, the relationship between the response and B is flatter.

Similar definitions of antagonism and synergism hold for the B-against-A plot.