Quote Originally Posted by flyingPenguin
How much do I need to win now to cover my draw? First thing that comes to mind is that it's the same as on the turn: $4 x 6 - $15 = $9. $9 x 2 + $15 = $33. This covers the turn bet, but not the flop bet.
The flop bet is "covered" by your estimation that if you hit the turn you would get paid off. When you are trying to decide whether you have odds to call on a missed turn you only need to take into account the size of the pot, the bet you are faced with and how much you expect to extract if you hit. Whether your flop call was + or -EV does not influence the turn decision - your turn and river decisions cannot make a bad flop call into a good flop call or vice versa, you should just try to maximise the value of the situation you are in regardless of how you got there.