This is helpful in explaining that every poker hand is practically unique, but less in explaining normal statistical variations in a player's winnings graph. An excellent tool to play with to figure these out is here:

ev++ Poker Tools :: Poker Variance Simulator

The relevant parameters are number of hands played, standard deviation and winrate, more than the number of possible combinations of starting hands.

For more insights about poker combinatorics and how to use them in play, see here:
http://www.flopturnriver.com/pokerfo...light=blockers