200 Participants completed 3 tasks (easy, medium, difficult) and a cognitive ability test. All variables are continuous (for the task I have the time it took each participant to complete each task, and the cognitive test's score). To sum, I have 1 within variable (task difficulty) and 1 between variable (cognitive ability). The task time in each task level are positive skewed.
My hypothesis is that there will be an interaction between task difficulty and cognitive ability. What would be more appropriate – Repeated measures ANOVA or Mixed models?