Use an interaction plot to show how the relationship between one categorical factor and a continuous response depends on the value of the second categorical factor. This plot displays means for the levels of one factor on the x-axis and a separate line for each level of another factor.
Evaluate the lines to understand how the interactions affect the relationship between the factors and the response.
No interaction occurs.
An interaction occurs. The more nonparallel the lines are, the greater the strength of the interaction.
Although you can use this plot to display the effects, be sure to perform the appropriate ANOVA test and evaluate the statistical significance of the effects. If the interaction effects are significant, you cannot interpret the main effects without considering the interaction effects.