@WayneB 2 times and it's an option to look at the changes but I didn't mention that to avoid making it more complicated - but an ideal full analysis of everything we have would include analyzing how the change in volume between these two years impacts/explains the change in performance. The tests are all the same for each subject and also for each of the two time points (there are a handful of different tests that everyone does at each timpoint, I thought about doing the same analysis once for each)