Question

Explain what it means when a significant interaction results from a two-way ANOVA T RBC 3 (12pt) T T T Arial

Answer 1

An interaction effect is a change in the simple main effect of one variable over levels of the second. An AX B or A BY B interaction is a change in the simple main effect of B over levels of A or the change in the simple main effect of A over levels of B. The change in the simple main effect of one variable over levels of the other is most easily seen in the graph of the interaction. If the lines describing the simple main effects are not parallel, then a possibility of an interaction exists. As can be seen from the graph of the example data, the possibility of a significant interaction exists because the lines are not parallel. The presence of an interaction was confirmed by the significant interaction in the summary table. The following graph overlays the main effect of Ability on the graph of the interaction. Mean Score METHOD Blue Book Computer None Some Lots ABILITY