Just What is EV?

Systine

I have seen the term "EV" used all over this forum, even ScottyZ described it in a thread, however I still don't understand it.

What exactly is it, and how do you calculate it? It is even an ongoing stat or is it only for a given tournament or session?

Thanks,

ScottyZ

EV stands for expected value. It's commonly used two different ways: to evaluate single plays, or as a numerical estimate of someone's longer term skill level. The first one is more commonly seen since it's normally easier to calculate.

The easiest way to think of EV (in the first sense) is that it's the long term average amount of money you would make (or lose) if you repeatedly made the same bet a large amount of times.

A very good example is given in one (or more) of Sklansky's books, and goes like this:

Suppose you are tossing a fair coin and betting $1 on the outcome. In the long run, you'll win half of the coin tosses. (This is equivalent to saying that the probability of winning each individual coin toss is 1/2.) You make $1 when you win and lose $1 when you lose. In the long run, you expect to be ahead $0. We would say your EV is $0. To a well informed gambler, this bet is (in most cases) a waste of time, since it has the same EV as belching and scratching yourself.

If someone is willing to pay you $2 every time you win and take $1 from you every time you lose, your EV is now +$0.50 per toss. Why? You still expect to win half of the tosses in the long run, so you can intuitively pair the tosses up into win & loss pairs. You'll be ahead $1 for every such pair of tosses, so your per toss expected win is +$0.50. A well informed gambler would (in most cases) set aside his gastro-intestinal diversions and put his jock itch out of his mind, and partake in this bet.

The second form of EV is normally difficult to calculate, and has more to do with longer term, or higher level decisions. As an example, if someone somehow knows that their EV at holdem was +$6 per hour (i.e. that's how much they expect to win per hour) but their EV at 7 card stud was +$8 per hour, they should play stud, all else being equal. Most calculations of this type of EV are either based on historical results (e.g. I've make $6 per hour in the past playing holdem, so I'd expect to have similar results in the future), or are simply a very rough estimate and are almost guesswork.

ScottyZ

Dave Scharf

Very well explained.

Unknown

it has the same EV as belching and scratching yourself.

A well informed gambler would (in most cases) set aside his gastro-intestinal diversions and put his jock itch out of his mind

Did Sklansky really say this stuff, ScottyZ, or have you taken some liberties here... I've read these passages about EV a while back. I'm not sure if it's from HPFAP or TPFAP, but either way, I don't remember any humour, or any real attempts at humour, from Mr. Sklansky.

If these are verbatim quotes, well, who knew! Sklansky has a sense of humour!!!

ScottyZ

No, these aren't verbatim. Basically the real content of the example is Sklansky's and the attempted humour was mine.

I believe the coin tossing EV example is from his tournament book (TPFAP).

ScottyZ

Unknown

Damn, I was hoping he made a joke or two in those otherwise serious books. An example of somebody who tries to be maybe a little too funny in an instructional poker book is Phil Hellmuth in 'Play Poker Like the Pros'.

No, I didn't buy it. My girlfriend bought it for me, because she didn't know any better. However, after leaving it sitting around for a while, I decided it would make for some very appropriate bathroom reading.

To amuse myself, I try to see how many sentences I can count in one sitting that end with an exclamation mark. Bonus points for two exclamation marks, and extra bonus points if the words before the exclamation mark(s) are: "And you win a big pot".

Regards,
all_aces

ScottyZ

Yeah, unfortunately it seems like Sklansky would rather make you cry than laugh.

"...you are not ready for this book. And you deserve to lose."

*sob*

ScottyZ

Unknown

Ohhhh yeah... I remember that line. It just jumped out of nowhere about two thirds of the way through the book, and made me feel like an idiot! "And you deserve to lose". DESERVE TO LOSE. As if he actually said that in his book.

He did get his point across, though, and I re-read the damn thing several times so I could face that line without feeling like a stuped.