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Martingale System - Proving it doesn't work

BTW, there is no need to double your bet.

If you never leave until you are ahead, you will always eventually get ahead. It does not really matter what the bet is (consistent, doubling, random, etc), eventually you will get ahead. If you always bet a dollar, it would be a drunkards walk problem. If you randomize your bet, it would be bizarre but eventually you will get ahead.

I would think that doubling provides an optimized solution but it is not the only one.

CBL
 
If the only way to win is to have infinite money, I'd have to wonder the point of winning $ if you have infinite $. :D
 
Thanks for all your replies, didn't expect so much useful stuff so quickly!

My argument against infinite money was that then you are not gambling - there is no actual deduction from your money when you lose. Does this sound reasonable?

The other method I have thought is to run a computer simulation on a modified roulette table, which pays out 2-1 on odds of 19/37 (e.g. the casino pays out on 0). With flat betting, the expectation is to gradually increase your money as time progresses. With the Martingale system, you can still easily lose your stake very quickly. To me this shows the riskiness of the system quite clearly - but would it convince any non-believers out there?

DrDave
 
DO NOT risk your friendship by opposing his idea!!!

I'm too dim to understand the mathematics.
Nevertheless I suggest you congrat him for finding such a great idea.

Tell him you are going to start a Martingale Charity fund under his name.
(1) Ask him for Commitment of 10% of his winnings every month.
(2) Offer your service as fund Administrator.
(3) Ask him for Immediate seed money to set that up the fund.
Plus to pay for other expenses such as an inauguration party to announce the set up of the fund. A min of $1000 cash should be in order. Anything less would cask doubt about his financial soundness.

Then wait as the fund grows.

And at the end of the year rejoice with the selected charity organisation for his contribution.

This way, everyone wins.

Ps. The fact that you need to post into this forum imply that you are too dim to be his financial guarantor. So stick to you simple administrative role.

Pss. I'm not sure why the people over here are so sceptical, but I sense your friend to be a lucky person. I wish him/her all the best.

Psss. My local charity organisation has been hit pretty hard by the Tsunami disaster. Since the disaster, the donation has been drawn away. Please send a $100 cheque soon.

I'm very serious!
 
What is most important?

(1) Your friendship with your friend.
(2) Your friend's money.
(3) Your friend's success.
(4) Your ego.
(That you can win the argument, and cobble your friend
up now that you are armed to the teeth with sharp logic and ugly truth)

By the way, this might be helpful.

Irony Games' Dice Server
http://www.irony.com/igroll.html
 
If the only way to win is to have infinite money, I'd have to wonder the point of winning $ if you have infinite $
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Yes, but once you start betting millions of dollars, they give you free drinks. And free drinks are free drinks no matter how rich you are.

CBL
 
Jyera said:
DO NOT risk your friendship by opposing his idea!!!
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If he's a real friend he should tell his friend when he's wrong, and give him evidence of it if he can. I would expect my friends to do the same, especially if my hard earned money was on the line.
If a friend won't oppose your ideas when they can seriously hurt you, they aren't real friends. If it's something inconsequencial, then of course it's stupid to make a big deal of it, especially if you've already had an arguement about it in the past. But if, as in this case, it's something that can really negatively affect your friend's life, then do it. In this case the risk to your friendship is a necessary part of being a friend.
And even if the friendship did fall apart, I'd hope that after he lost all his money that gambler might realise that you had his best interests at heart all along.
 
By the way, if none of the above works, all you have to do is make a little gambling program on your computer that simulates roulette or whatever game he wants to play. Ask him how much money he expects to win with the system, and see if he can do it with your program.
Let him start with exactly the amount of money he is planning on spending on this trip. The good thing about that would be that he won't have to risk his own money to do so.
If he gets it into his mind that he just needs more money, you can have him try for the same results with any arbitrarily high amount of money you like.
The reason I suggest this is that it's a strong demonstration that doesn't require any understanding of the mathematics on his part.
 
Originally posted by jj
I think you need to calculate the handle and the expectation before you pronounce this a "sure win" because it's a "sure lose".
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What does "handle" mean in this context?
 
Originally posted by CurtC
It doesn't even work with infinitely many runs. How many negative-expectation bets must you sum to achieve a positive-expectation overall? The answer sure ain't infinite.
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No fixed number works. But "as many as it takes in each case" works, provided I have enough money to place as many bets as it takes.

Following a martingale system in practice is certainly a bad idea, because I don't have an infinite amount of money, and no matter how much money I do have, some cases will require more than that amount.
It is a little pointless to talk about the expected value for a sequence of bets that have already occurred, [...]
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Yes, exactly.
[...] but you'd have to consider doing that same sequence again and again, and comparing that.
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Why should I consider how much money I'd make by doing that same sequence again and again, if the martingale system I'm following tells me not to actually do that same sequence again and again? If I want to evaluate a martingale system, I should consider how much money I'd make if I followed the martingale system.
 
Originally posted by CBL4
BTW, there is no need to double your bet.

If you never leave until you are ahead, you will always eventually get ahead. It does not really matter what the bet is (consistent, doubling, random, etc), eventually you will get ahead. If you always bet a dollar, it would be a drunkards walk problem.
Click to expand...
If the odds of each bet are exactly 50:50, you'll eventually get ahead by betting the same amount each time. But if the odds are even slightly against you, you might not ever get ahead that way, though you will eventually get ahead by doubling your bet each time.
 
Originally posted by 69dodge
If the odds of each bet are exactly 50:50, you'll eventually get ahead by betting the same amount each time. But if the odds are even slightly against you, you might not ever get ahead that way, though you will eventually get ahead by doubling your bet each time.
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Good point that I missed.

Enough time might guarantee overcoming the bias towards losing. But then again it might not. It probably depends on the bias toward losing but I am not even sure of this. Perhaps even the slightest bias would prevent the guarantee. My math is way too rusty to figure it out.

CBL
 
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