How do you explain Martingale to someone who doesn't understand EV?

AlmightyJay · #1 10-24-2005, 08:12 PM

I'm having an argument with some people who claim that Martingale works, in theory, if you have an infinite bankroll. I'm trying to explain to them that because each bet has -EV, it doesn't matter how much money you have, you're still doomed to failure. (I'm correct, right? They have me doubting myself)

However, they're clueless about what EV means, so I can't argue this way. How do I explain why it doesn't work without using EV?

skiier04 · #2 10-24-2005, 09:53 PM

If they truly were to have a bankroll of "infinant" dollars they would eventually win and show a profit.

If they just have a very large amount of money explain to him that the times he wins he will win a very small amount, but the times he loses say 7 times in a row he will lose pretty much everything. And this will happen.

#3 10-24-2005, 10:06 PM

Tell them you realized it does work and to go do it. After they lose all their money you can say sorry...I thought it worked. hehe

flatline · #4 10-24-2005, 10:26 PM

As has been discussed many times here, Martingale works with an infinite bankroll and infinite table limits. Of course this situation never exists.

Double Down · #5 10-24-2005, 10:49 PM

I hope to not start a huge thread on Martingale again, but isn't it mathematically shown that even with infinite br and table limits that it still fails because of the chance of the infinite losing streak?

flatline · #6 10-24-2005, 11:42 PM

The chance of an infinite losing streak is zero.

Double Down · #7 10-25-2005, 12:44 AM

Yes, you're right. Is that because the odds of having at least one win is .9999 etcetera and that number is the same as 1?

Mathematically it makes sense, but can it be explained theoretically? It would seem to me that in the land of infinity it should be possible.

The Goober · #8 10-25-2005, 06:54 AM

Think about it this way...

Suppose you take your infinite bankroll and decide to play for a set period of time. You'll play strict martingale and stop at the predecided time regardless of what happens. What are the chances that you'll finish a winner? Well, it'll work out that there will be a largish chance that you will be a small winner, and a smallish chance that you will be a big loser (because you stopped during a string of loses). Do the math, and your estimated EV at the stop time will be exactly your EV for the game (given you average bet size).

Of course, that's not really playing with an infinite bankroll - if you have a hard time limit, you have a hard bankroll limit too (how much it would cost you to lose every roll for the whole length of time). If we take it as a given that martingale doesn't work for a finite bankroll, but claim that it does work with an infinite one, then we must concede that we might need an infinite amount of time to get to our goal. So now it reduces to: "you can make a profit martingaling with an infinite bankroll, but you have to gamble for an infinite amount of time, and if we stop and check your progress at any point, more likely than not, you will be losing." That doesn't really sound like you are making a profit at all.

Another thing to think about. Suppose we took our infinite bankroll and simply doubled our bet every time. This strategy is just as good as a martingale one: At any one time we are more likely to be behind than ahead, but more likely that not will we be ahead again as some point (although it might take an infinite amount of time). Any betting system works this way as long as you increase your bet size consistently so that the std. deviation will overwhelm your expectation.

tomdemaine · #9 10-25-2005, 09:02 AM

[ QUOTE ]
The chance of an infinite losing streak is zero.

[/ QUOTE ]

as is the chance of an infinite bankroll. Point proven I'll take my prize to go please [img]/images/graemlins/smile.gif[/img]

Komodo · #10 10-25-2005, 09:15 AM

</font><blockquote><font class="small">Svar till:</font><hr />
As has been discussed many times here, Martingale works with an infinite bankroll and infinite table limits. Of course this situation never exists.

[/ QUOTE ]

No. It has been discussed before here. If you get an infinite bankroll, there is still a small chance to you lose in an infinity, which is enough for the martingale system to fail.