The F test in ANOVA is equivalent to a (21) test even though the rejection region appears only in the upper tail of the distribution. This is due to the squaring of all the values that makes it impossible to have a negative value for F. CHAPTER 18: ANALYSIS OF VARIANCE (TWO WAY) Key 'Ibrms TWO-way ANOVA A more complex type of analysis of variance that tests whether differences exist among population means categorized by two factors or independent variable. Main effect The effect of a single factor when any other factor is ignored. Simple effect The effect of one factor at a single level of another factor. Interaction The product of inconsistent simple effects. Ten Review In two-way AN OVA, there are four different types of means. Column means represent the effect of one variable when the other is ignored. In the text example, column means represent reaction times for each number of confederates present when (1) is ignored. Slight difference among these column means could be attributed to (2) . More substantial differences reect the main effect of the number of confederates on reaction time. In ANOVA, the effect of a single factor, when any other factor is ignored, is the (3) . Row means represent the reaction times for gender when crowd size is ignored. Again, slight differences could be attributed to chance, but larger chances reect a (4) of gender on reaction time. The cell means, also referred to as treatment-combination means, reect any effect due to the interaction of the two factors being studied. The final average of the column means or row means equals the overall or