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Math odds that look good but aren't


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I was just helping my son with some of his probability homework when I remembered reading of a clever game a gambling operator ran that gave a player even odds of the player rolling two dice to get a double 6 in 19 rolls.

The average player thought he had the better of the deal with a 19/36 chance of winning or a 2.7% edge.  Actually, the odds of not rolling a double 6 in 19 rolls is 1- (35/36 to the 19th power) or 58.55 so the house actually had a huge 8.55% edge.  

I know that gambling inherently takes advantage of players' lack of math skills, but this seemed a clever way to take advantage of people that knew just enough about math to make them actually think they had the edge.  They'd keep playing figuring they were on a cold streak and all they had to do was wait for the law of large numbers to kick in.

Anyway, not much point to the post other than I always found this type of shit fascinating.  

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On 4/16/2020 at 12:48 PM, Not a cat said:

I was just helping my son with some of his probability homework when I remembered reading of a clever game a gambling operator ran that gave a player even odds of the player rolling two dice to get a double 6 in 19 rolls.

The average player thought he had the better of the deal with a 19/36 chance of winning or a 2.7% edge.  Actually, the odds of not rolling a double 6 in 19 rolls is 1- (35/36 to the 19th power) or 58.55 so the house actually had a huge 8.55% edge.  

I know that gambling inherently takes advantage of players' lack of math skills, but this seemed a clever way to take advantage of people that knew just enough about math to make them actually think they had the edge.  They'd keep playing figuring they were on a cold streak and all they had to do was wait for the law of large numbers to kick in.

Anyway, not much point to the post other than I always found this type of shit fascinating.  

I think I disagree with your math work there Lou.

The bolded should read

Quote

Actually, the odds of not rolling a double 6 in 19 rolls is (35/36 to the 19th power) or 58.55 so the house actually had a huge 8.55% edge.  

(take out the 1-)

1-(35/36)^19 are the odds of rolling a double 6 in 19 tries, which equals .4148

 

but you are right, house has a 8.55% edge.

 

 

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I played in a NLH poker tournament the other day, and this guy called a 4-bet shove preflop with 5-5 against K-K.

No 5 comes and he loses the pot. He then tried to explain his actions by saying he "lost a coin flip."

"Coin flip?" I say. He says "Yeah, you either win or you don't."

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32 minutes ago, Bookman said:

I played in a NLH poker tournament the other day, and this guy called a 4-bet shove preflop with 5-5 against K-K.

No 5 comes and he loses the pot. He then tried to explain his actions by saying he "lost a coin flip."

"Coin flip?" I say. He says "Yeah, you either win or you don't."

Donkeys are never good at math. 

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1) Monty Hall, it amazes me that so many people still don’t understand it after years of being taught in schools.

2) not gambol related: but I loathe the way news covers percentage increase and decrease.

“Median housing prices fell 25% from 2008 to lows last year, but largely recovered, rallying 18% since the valley” No Mr. Editor, 25-18 = 6 doesn’t mean they’re at 94% of their initial price. 0.75 x 1.18 = 0.885. But simpler than that is the amount of times you see 100% or 200% increases misused in print.

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On 8/27/2020 at 6:11 PM, slorch said:

6.  Almost 50 percent of all marriages in the United States will end in divorce or separation.

I remember getting in an argument with my sociology teacher in high school about this. I went to high school in Arlington and the population had grown from 79k to 275k over the last 7 years. She said 90% of marriages end in divorce in Arlington based on the number of marriages and divorces in Arlington in the last year. I asked her how many of those divorces were from marriages that happened outside of Arlington from people that moved here and how many years of marriages are we comparing to this years numbers of divorces. She got really angry. 

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