I've noticed with certain datasets that when I try to do an anova and test for main effects and interaction for two explanatory variables, sometimes the main effect results are given but not the interaction results. For example,
ex1 = aov(Score ~ var1*var2, data=myData) summary(ex1) gives me only the main effects for var1 and var2, but not the interaction. I also tried ex1 = aov(Score ~ var1+var2+var1:var2, data=myData) summary(ex1) but it still only gives the main effects. The only way I can get the interaction results is if I test for ONLY that, e.g. ex1 = aov(Score ~ var1:var2, data=myData) summary(ex1) Why would the interaction not be tested in the first two examples? Thanks, Gabe [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.