I have a 2 level repeated measures DV of accuracy, and a covariate of response bias. As response bias increases, accuracy level 1 increases while level 2 decreases. I want to see if there is a difference in the means of the groups after controlling for response bias.
I can't do it with an ANCOVA. Can I just manually calculate expected values based on a regression equation, and run an ANOVA?
I'd like to do it in R or SPSS, so specifics for either would be welcome, but not necessary.