Interaction plots are common to detect interactions in two-way ANOVA. The plots depict the mean for the first factor relative to the response variable grouped by the second factor. #diagram Where the lines are parallel, an interaction is not indicated. If the lines cross, an interference interaction may be present. If the lines diverge, a reinforcement (synergistic) interaction may be present. Because interaction plots are plotted from sample data, they do not necessarily reflect population level trends and so should be interpreted with caution.