OK I'll try again
I have participants in three groups.
Each participant has looked at 30 sets of stimuli and rated them on a scale 1-7
Each stimuli has a value is strength, this may be the same value for different stimuli or different for each.
I need to use Ancova to see if the stimuli strength predicts the rating they get depending on the group the participants are in.
Is that any better ?
The examples I can find are more like
There are three groups of mothers, group 1 drink milk, group 2 drink scotch, group 3 drink water, what effect does this have on a babies birth weight
Hope that is clearer