It would be interesting to post this sort of question into the forum for suggestions in the game. I wouldn't know how to word it but if one were to simply ask for the data of active users according to X hours per X days/weeks, then we could start to get some info. On top of that, you would want some that shows their highest finished song and possibly the song difficulty that they seem to have mastered. (ie a bunch of S's A's or such at a certain difficulty).
This information would of course just be for the "kicks and giggles" but it would also show some interesting insight to what people are able to accomplish. We know that "average" in this game has too many variables. What if instead we had the information to simply look for what we wanted. I would love to know what difficulty active users are able to accomplish. This would then tell me if I were getting better at songs at an above or below average rate. Sure, I have played for 3 weeks and can finish some 4 star songs, but where are most people in that amount of play time?
Too many variables.
Again, what if we polled this to get it added into the game?