Interaction Effects: Their Nature and Some Post Hoc Exploration Strategies.

This paper reviews the basics of the elusive but important concept of the interaction effect. The analysis of variance (ANOVA) interaction effect is defined both conceptually and mathematically. Common errors in interpreting interaction effects are discussed, and appropriate strategies for achieving post hoc understandings of the origin of detected interaction effects are presented. It is important that researchers in the fields of education and psychology learn to report and interpret interaction effects correctly when using an ANOVA design. (Contains 16 references, 4 tables, and 3 figures.) (Author/SLD)