How do I measure the cost of mistakes ?

[muzungu]

damn, mark, so many responses and no one gave you a good answer (well, except for thabadguy).

You are asking a few different questions here.

The simplest one is the cost of a given mistake. Looking at this from a Fundemental Theorem of Poker perspective (if you don't know what this is, read Theory of Poker), you can look at the cost of a mistake by comparing your equity when you put $ in to how much you put in.

So, you get your KK all in preflop with his AA for $500 apiece. You win around 18% of the time.

Your equity here is .18($1000) = $180. You put in $500, so you just made a $320 mistake.

Now you might object, I couldn't know he had AA. Similarly, in any situation where you call on the river and lose, this sort of calculation would say you made a mistake, as your equity is 0.

The answer is that you can make the same calculation using hand ranges. So, in the KK example, say you think his range is AA-QQ. Here, your equity is around $500. You chop with KK, and get from QQ about what you lose to AA. Note that he can have QQ and AA equally often. If we throw AK in, your call is +EV... and so on.

The skill in all this is trying to make your estimate of his hand range as accurate as possible. So, perhaps you think he can have AA-QQ or AK, making your call with KK a winner, whereas he actually would only go all in with AA (making you a $320 loser).

As you get to know your opposition better, and as you improve as a player in general, your estimates will be closer to their actual holdings, allowing you to make fewer mistakes.

That should about cover it.

-muz