None of the above
My advice, search for "mean", "median" and deviation in Math forum
and you will gte >200 great questions that will cover anything and everything you will need for GMAT.
Also each challenge has 2-3 very good questions on Meam/Median/SD.
You want it, we got it
"To dream anything that you want to dream, that is the beauty of the human mind. To do anything that you want to do, that is the strength of the human will. To trust yourself, to test your limits, that is the courage to succeed."
- Bernard Edmonds