I'm struggling about a statistics problem regarding combining several individual dependent variables into one.
I'm doing Repeated ANCOVA for behavioural data (numerical). However, since some variables may be working together, I want to combine them and create a new dependent variable. The problem is that those variables are not necessarily significantly correlated and taking the mean seems not a very good solution.
So my question is, in this case, what is the best way to combine those variables? Is taking the interaction term better? Do I need them to be significantly correlated?
Thanks very much!