![calculate degrees of freedom for factorial anova calculate degrees of freedom for factorial anova](https://cdn.numerade.com/ask_previews/8c3d858a-ea14-4a4f-b5d2-716f4eb135f0_large.jpg)
![calculate degrees of freedom for factorial anova calculate degrees of freedom for factorial anova](https://i.ytimg.com/vi/98yMBOl0vxE/maxresdefault.jpg)
To get some idea of whether an interaction is actually happening here, it helps to plot the various group means.
![calculate degrees of freedom for factorial anova calculate degrees of freedom for factorial anova](http://mondaywww.statisticslectures.com/images/rmanova3.gif)
The ANOVA that we developed in the previous section does not capture this idea. To give a more concrete example, suppose that the operation of Anxifree and Joyzepam is governed quite different physiological mechanisms, and one consequence of this is that while Joyzepam has more or less the same effect on mood regardless of whether one is in therapy, Anxifree is actually much more effective when administered in conjunction with CBT. Several examples of an interaction effect with the context of a 2 x 2 ANOVA are shown in Figure ?. An interaction between A and B is said to occur whenever the effect of Factor A is different, depending on which level of Factor B we’re talking about. Why not? Well, so far we have the ability to talk about the idea that drugs can influence mood, and therapy can influence mood, but no way of talking about the possibility of an interaction between the two. However, they are not the whole story, and the ANOVA model that we have been talking about up to this point is not sufficient to fully account for a table of group means. The four patterns of data shown in Figure ? are all quite realistic: there are a great many data sets that produce exactly those patterns. \)įigure 16.5: Qualitatively different interactions for a 2imes2 ANOVA Figure 16.6: Qualitatively different interactions for a 2 i m e s2 ANOVA Figure 16.7: Qualitatively different interactions for a 2imes2 ANOVA Figure 16.8: Qualitatively different interactions for a 2imes2 ANOVA