Is there any EV or mathematical advantage of running it twice?

Like lets say I'm a 60/40 favorite with two cards to come. I'm one of the guys who never run it twice. Is there any scenarios where its advantageous to run it twice?

reduces variance thats about it....

Advantageous isn't the right word. I assume you use it in that it would increase your equity or something but it can't. It just reduces variance as riley said. In a case such as a 60/40 you just have a 60% chance each time, it doesn't really change.

I always run it three times if I'm ahead. Gives me a better chance to win more than half!

What does 'run it twice' mean?

Steve

the cards are dealt 'twice'. ie. if two players get it allin on the flop, they can 'agree' to run it more than one time.

one time or 3 times for me, running it twice is bullshit in most cases. because I don't want to split the pot in a flip situation for example.

Thank you, Sir. I hadn't heard of that before.

Steve

Do any online poker rooms have this as an option? I like it

yes when you are a 60/40 dog

why? You still can win the pot 40% of the time either time.

Usually if all the money goes in and the underdog has tonnes of equity then the underdog is on a draw.

So the underdog then becomes a favourite to win it once. (more cards = more equity for a draw .. think about what happens to a FD equity between the flop and the turn).

Sorry, I'm pretty sure the expected payout doesn't change. Like someone said earlier, all that changes is that the variance is reduced.

It definitely favours big draws but has no effect on made hand vs made hand.

It turns the draw from an underdog overall closer to a coinflip.

For one thing the second card to be dealt (assuming the first didnt hit the draw) is now dealt from a deck that contains one less non-flush card than before. Its going to alter the probabilities slightly and if you are behind its altering them slightly in your favour.

So the guy on the draw is fractionally less likely to loose twice with a FD when running it twice than he would be to loose 2 all-ins with 2 FDs that were run once.

Assuming the FD misses the first time the ratio of flush to non flush cards has increased slightly.

Right. Better to lose it all outright.

Are you suggesting that the second run doesn't include the cards that were dealt from the first run? Surely that isn't true?

I was under the impression that the two runs were completely independent trials, each with the exact same probabilities. For example, if we're 60/40 favored to win a $1000 pot, our expected payout is 60% x $1000 = $600 (assuming no splits are possible here) without running it twice.

Now if we run it twice, the probability of winning both trials is 60% x 60% = 36%, and the probability of losing both trials is 40% x 40% = 16%. This leaves 48% that we each win one trial and split the pot. Therefore, our expected payout is 36% x $1000 + 48% x $500 = $600 again.

The only difference is that our variance is reduced, since almost half the time we don't lose any money, instead of the all or nothing nature of the standard deal. I'm too lazy to compute the variance, which is simply the square root of the sum of the squared deviations of the possible outcomes from the expected outcome.

Or am I missing something, either subtle or obvious?

The second run does not include the cards from the first run.

If say, the flush draw hits on the first run, the second run would have 1 less out.

Thats it.

The effect probably isnt as great as I first thought (because the random example I though of was KK vs a7s on a 2tone board on the flop.. roughly 52:48 in favour of KK.. with 2 cards to come I estimated that the A7 could actually become a favourite on the second run.. assuming it missed the first because in this case there 12 outs and 2 non-outs have been removed prior to the second run.)

I haven't seen it run twice on line (perhaps they do it differently) , but live... the leave the first run cards on the table whilst running the second.. so yes the second run would not include the cards from the first run.

there is a 'run it twice by default' option on full tilt.

You're paying more rake when you're running it twice.
There's also the probability that something like this happens:

If they'd run it once, he'd still have lost the whole pot, so what's the difference?

It's 10000x more of a suckout, hence, more tilting
EDIT: Actually, it's 13.5 times more of a suckout, but still, you get the idea

Full Tilt has it at 200nl and above, but not at 100nl and below. It requires both players to have chosen to run it twice, and it costs an extra buck in rake.