I have a friend who is a winning midstakes player who has become convinced that following a friend of a friend's betting system is +ev. He is not betting so big he can lose his roll, so normally I would just call it entertainment value, but when I hear about the -ev things he is doing (ex: buying 2 points just before the game goes off) I hate to see him get raped, and I feel I must try harder to talk him out of it, so I need some forum help with ammunition. I think he has just not been exposed to many touts before. His reasoning for doing it was that if the system has only a 10% chance of working as well as it says it does then it is worth it to give it a shot. I made a little headway hammering on sample size, but not enough. It is the standard "this system hits 75% of the time over the last 12 years" line, so I feel I may do more damage by finding a bunch of other systems that hit some huge percentage over many years and showing him that they don't perform that well over the next few months. Is there a good website that has this stuff? The system "makes sense" to him (martingaling on teams to win at least one out of 3 games or something like that), and I think this is the main area he is getting a mental block. I appreciate any info you guys can give me!

Can you do an EV calculation to show him it has -EV?

Here's some stuff: http://wizardofodds.com/gambling/betting-systems/

I truly doubt he can be convinced. It is amazing how many otherwise seemingly smart people fall for crap like this and can't see the flaw in betting systems. I have never really had any success in convincing someone who thinks they have solved roulette or any other nonsense like that. They just don't get it. This includes some people who generally don't seem to be idiots at math incredibly enough. I really don't understand it....still.

well, on the buying points front, show him a half-point calculator.

the rest? sucker born every minute right?

If the bets aren't +EV of themselves, martingaling can't make them more +EV. Surely you can explain that - 'Oh, you bet $x so you lost, but if you bet $xx you would have won?

Or the Universe knows that you only bet $x last time so betting $xx is a sure winner, is that it?'

I think the basic test should be do they agree with 'If the bet wins, the odds were good.' If they say yes, just walk away. There is nothing you can do.

You can start offering bets/taking action.

Std advice for anybody we know who wants to suddenly start betting their 'system' amirite?

wait you have to explain what sample size means to a winning midstakes player? are you sure hes a winner?

Really, you could say the same about anyone who thinks martingaling makes a bet +EV.

This is definitely the play here. Upset I didn't think of it earlier. Thanks guys!

I'm finally getting around to making him an offer to book his action. Good thing I didn't do it earlier because he was up 11k at one point and he's currently up 6. He's betting on MLB now too. He's made about 200 bets total, and thinks that this is a huge sample. I want to do something like giving him 1% of his net winnings on top if he wins, but he didn't seem to thrilled with the extra hassle. I guess we would set up a sportsbook account that he will bet on at 1/100th of the amount that he actually wants to book, and then multiplying the end balance by 100 to see how much he is up or down with me. I'm trying to figure out what the max % of his net I could offer him would be. What do you guys think?

It all depends on the time period. A 50% rebate (on the net) once a year could be better for you than a 2% rebate once a week.

I've never bet with rebates, but there have been threads about some deals like that.

What he said. do the math. It's not always obvious.

I spent an hour mucking about with binomial distributions in a spreadsheet, and it seemed that if he bets another 200 games my edge is very high, so I gave him 30% on top of the winnings and nothing back on the losses on all bets through the end of the year, which will probably be a bit more than 200. If my edge is 2.5% per game, he's only 26% to show a profit over 200 games and his average profit when he wins is about 5 bets. He is betting on 3 books: pinnacle, thegreek, and 5dimes. This gives me the idea that maybe I should offer to give him a higher % of winnings if he only takes action on one book instead of shopping for the best line on all three. Can someone give me an estimate of how much this would be worth? +35% of winnings? 50%? I'm inclined to think it is very high, but it's been a while since I bet these books heavy, so I don't know how much he can save by shopping them.