I have 3 within-subject factors, namely
offset (1px, ..., 5px),
side (left, right) and
color (red, green), which define the characteristics of the stimulus in a reaction time experiment. The DV is reaction time
RT. The design is fully balanced.
I ran a repeated measures ANOVA in R, like this:
options(contrasts = c("contr.helmert", "contr.poly")) simon.aov <- aov(median.RT ~ color*side*offset + Error(VP / (color*side*offset)), data=dfa)
The results revealed a significant main effect of the
color, as well as a significant interaction
color x side and a significant 3-way interaction
color x side x offset.
My primary focus lies on the interactions. Specifically, I want to know on which of the 5 offsets (i.e. on which levels of the third factor) the 2-way interaction
color x side reaches significance.
I am by no means familiar with post-hoc contrasts and multiple comparisons, but this question is the gist of the thesis that I'm working on. So my progress depends on an adequate test to examine this question.
I highly appreciate any help on which test to run, and how to do this most efficiently in R.
I'm sorry I didn't provide any plots earlier.
@John: Here is the plot you requested.
However, I believe, that this following plot rather clarifies my question:
It seems like there is no
color x side interaction at the first 3 levels of
offset, but this interaction emerges at
offset 4 and 5. This is what the plot seems to imply, however I don't know how to prove it statistically.