These study tips are designed to clarify key points and help you to avoid errors that students commonly make. Review the Tips for Success as you study each chapter and review them again after you have studied each chapter.
- What you need to have mastered before starting this chapter: For the first part of the chapter, you need to have read and understood Chapters 1 through 9; for the Advanced Topic sections of this chapter, you also need to have mastered Chapter 9’s Advanced Topic material on the structural model in the analysis of variance.
- Remember, you determine if there is an interaction effect by looking at the pattern of cell means. There is an interaction effect if the pattern of differences in cell means in one row is different from the differences in cell means across another row.
- You determine main effects by looking at the marginal means. The marginal means are the means in the “Overall” columns and rows in Tables 10-4 and 10-5 on pages 391 and 392. There is a main effect for a variable if the marginal means for that variable are not the same.
- Study Figure 10-11 (p. 407) very carefully: it is the best way to understand and remember the structural model for the two-way analysis of variance.
- When figuring the deviation for the interaction effect, keep close track of the signs of the deviations you are subtracting and remember that this interaction deviation, prior to squaring it, is figured from the original unsquared deviations, not the squared deviations.
