Some operator ideas: mean and MAD
The mean is just the average
The MAD (or mean absolute deviation) is way more fun. You probably know about this already, but to find it first you find the mean. Then you find how far away each original number was away from the mean (as an absolute value) and find the mean of those.
Maybe a bit too much math
Wait, what am I saying!? I'm on a website devoted entirely to math puzzles!
I also saw somewhere in this forum another idea, by fnord - "straights." Here it is:
viewtopic.php?f=2&t=705&p=5588&hilit=straights#p5588