[gaming_mouse]

[ QUOTE ]
to keep it simple lets say i pick 4 teams, 1234, all straight 11$ to win 10$ for 44$ to win 40$ total.

I have 4 parlays
teams 123 $11-$66
teams 124 $11-$66
teams 134 $11-$66
teams 234 $11-$66

so any 3/4 nets $33 profit. 4/4 nets $264 profit. and anything else I lose $44

[/ QUOTE ]

So let's say you can pick a team correctly with 55% accuracy.

EV_straight_wagers = 4*(10*.55 + (-11)*.45) = 2.2

Now let's get the EV for the parlay.

The chance that you choose exactly 3 teams correctly is:

4*(.55)^3*.45 = 0.299475

All 4 correctly:

(.55)^4 = 0.09150625

Thus:

EDIT AGAIN (I was confused by how the odds were working. I'm assuming now that you risk 11 to get 66 in profit):

EV_parlays = (66-33)*.299475 + (66*4)*0.09150625 + (-44)*(1-0.09150625-0.299475) = 7.2435