I'm measuring "number of interactions with a device" (it's an exercise used with autistic children, and the more interactions they have with this device on a daily basis, the more they have improved in their skills). So basically, I have totals for every day for about 2 years, and I want to compare the average number of interactions with the device in the first year to the average number in the second year. Is a t-test a valid way to do this? Would it be a paired samples t-test given that it's the same person in the first and second year? Or, do I use a totally different test, given that this is a single person over time?