I am working with some educational research, on a study with learning as a dv (scored on a continuous scale) over four times. Additionally, I have a between groups variable (condition) and a covariate for each time. I want to run a repeated measures ANCOVA so that I can see the treatment effect for each condition at the four times, controlling for prior ability with the pretest covariates. My problem is that at each time they had a different pretest, so I want the covariate to only be applied to the specific time. In other words, pretest one should only covary with time one, pretest two with time two, and so forth. I am using SPSS to run my analysis, and I can figure out how to set up the covariate for this situation. Any suggestions?
Thanks for your help!!!