More complex example
Your stack: 2000
Villain's stack: 1500
Blinds: 25/50
You have QQ in MP. Villain is SB. Folded to you, you raise to 150 preflop, folded to Villain who calls, BB folds. Two players see a Ts8s4c flop. Villain checks, you bet 250, villain checkraises all-in.
What's the EV of folding? What's the EV of calling? The EV of folding is easy. If you fold you lose 400 chips, so EV(fold) = -400
Working out the EV of calling is more tricky. First we have to assign a range of possible holdings to Villain. Let's use something like this. We're assuming Villain is a reasonable player for the sake of simplicity.
(I got the win %s from PokerStove. If you're serious about stats in poker, get it, it's free)
AA, KK - Unlikely (surely villain would have reraised preflop), but maybe Villain has played AA/KK trickily.
5% chance, Hero is 10% to win.
JT+ - Plausible, makes some sense given the action and there are many possible combinations of top pair hands.
30% chance, Hero is 80% to win.
TT, 88, 44 - Again, reasonable possible holdings. Fewer combinations, but it's probably more likely villain plays a set like this on the flop than top pair.
25% chance, Hero is 10% to win.
AsJs+, KsJs+, QsJs - Again, reasonable to assume villain would call with these preflop and semibluff your c-bet with a flush draw and overcard(s) on the flop.
30% chance, Hero is 70% (average) to win
Nothing - Harrington says allow a 10% at least that a player is totally
bluffing. We'll use the minimum here, as it's unlikely Villain would want to commit all his chips on a total
bluff.
10% chance, Using AJo as a 'control' hand (as the probability of villain bluffing with total junk {53o etc} is tiny), Hero is 82% to win
So...
EV(call) = (1550*(0.05*0.1)) + (-1500*(0.05*0.9)) <--- This is for the occasions Villain has AA/KK
+ (1550*(0.3*0.8)) + (-1500*(0.3*0.2)) <--- If villain has JT+
+ (1550*(0.25*0.1)) + (-1500*0.25*0.9)) <--- If villain has TT, 88, 44
+ (1550*(0.3*0.7)) + (-1500*0.3*0.3)) <--- If villain has AsJs+, KsJs+, QsJs
+ (1550*(0.1*0.82)) + (-1500*(0.1*0.18)) <--- If villain is bluffing (using AJo)
EV(call) = (7.75 - 67.5) + (372 - 90) + (38.75 - 337.5) + (325.5 - 135) + (127.1 - 27)
= +214.1
In other words you will end up with 214.1 chips more that you started the hand with on average if you call. If you compare with the EV of folding.
EV(call compared with folding) = 214.1 + 400 = 614.1
In other words you end up on average with 614.1 chips more than would have had by folding. Sometimes what seems like a -EV decision can actually be a +EV decision when compared with the alternative.
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Taking a look at a bit of the calculation in depth.
(1550*(0.05*0.1)) + (-1500*(0.05*0.9)) <--- This is for the occasions Villain has AA/KK
Here the 1550 (villain's stack of 1500 + big blind of 50) is your gain if you win, the 0.05 is the probability Villain has AA/KK and the 0.1 is the probability you win the hand (and thus gain 1550 chips). Constrastingly the -1500 is your gain (loss) if you lose, the probability villain has AA/KK is still the same, and the 0.9 is the probability that you lose the hand (and thus lose 1500 chips).