why double down inreases advantage

[psyduck]

Let's pick 11 vs dealer's 5. I understand why double down wins more money because I double my bet. However, if I do not double down, I will certainly hit and most likely end up taking one more card just like double down. So where does the extra advantage (EV) of double over not double come from?

 

[Koz1984]

The extra money you win on a DD.

 

[psyduck]

The extra money you win on a DD.

I understand that part. I was talking about the extra advantage measured as percentage of total bet. Let's say the advantage is 7% for not doubling. Why does doubling have say 7.2% advantage?

 

[Mewtwo]

I understand that part. I was talking about the extra advantage measured as percentage of total bet. Let's say the advantage is 7% for not doubling. Why does doubling have say 7.2% advantage?

When doubling with some hands, there are situations where you may want to take another card afterwards but you can't because you doubled, and that could be the difference between winning and losing a hand. If the amount of money you lose from these situations is exceeded by the extra money you win from the doubles you do win, then that's where the extra percentage advantage is coming from.

 

[Blue Efficacy]

I understand that part. I was talking about the extra advantage measured as percentage of total bet. Let's say the advantage is 7% for not doubling. Why does doubling have say 7.2% advantage?

It's really easy. You're putting more money out in a situation where the player has an advantage.

 

[Sucker]

I understand that part. I was talking about the extra advantage measured as percentage of total bet. Let's say the advantage is 7% for not doubling. Why does doubling have say 7.2% advantage?

In this case, the advantage is measured as a percentage of your ORIGINAL bet.
If you bet $10 and don't double, you've earned 70 cents, or 7% of your total bet. If you double, your advantage is only 3.6%, but because your total bet size is $20, you'll earn 72 cents, rather than 36 cents.

So you are right, doubling DOES cause your advantage to go down, but as long as it's more than 1/2 of the advantage you have when you don't double, it's correct to double.

 

[bj bob]

I understand that part. I was talking about the extra advantage measured as percentage of total bet. Let's say the advantage is 7% for not doubling. Why does doubling have say 7.2% advantage?

I think you're looking at it the wrong way. Let's take your example of 7% on a straight hit. If your original bet were $50, then you would expect an advantage of $3.50. If you double that bet, however and your advantage drops to 4%, you now have a total bet layout of $100, so your expected win amount is $4.00, a smaller amount per bet, but more expected $ to be won in total. Comprende?

 

[psyduck]

It's really easy. You're putting more money out in a situation where the player has an advantage.

I know that. I am asking why the advantage gets higher when you double.

 

[psyduck]

So you are right, doubling DOES cause your advantage to go down, but as long as it's more than 1/2 of the advantage you have when you don't double, it's correct to double.

Sorry, but I did not make that statement.

I was running some simulations to determine index plays. I noted that the index for double down is based on when you have higher advantage than not double down. But I cannot figure out why double down can increase advantage (my understanding of advantage is a certain percentage of your total bet).

 

[psyduck]

If you double that bet, however and your advantage drops to 4%,

Why the advantage drops just because I doubled? In the case of 11 vs dealer's 5, both hit and double are likely to end up getting one card - the same play. It seems to me the advantage should be the same.

 

[Sucker]

I know that. I am asking why the advantage gets higher when you double.

Perhaps we're not making ourselves clear. The advantage does NOT get higher when you double, and in fact it goes DOWN. It's the money EARNED that goes up.

Would you rather be betting $50 with a 3% advantage, or $100 with a 2% advantage? In that latter, the ADVANTAGE is smaller, but the EARN is higher.

 

[psyduck]

Maybe qfit or other program designers can explain

Apparently the index assigned to double down is determined by when double down has higher advantage than not double - something I do not understand.

 

[psyduck]

The advantage does NOT get higher when you double, and in fact it goes DOWN.

Why down? Isn't advantage profit/wager? When you double, you increase both profit and wager by the same factor and therefore advantage should stay the same. Am I missing something?

 

[Sucker]

Why the advantage drops just because I doubled? In the case of 11 vs dealer's 5, both hit and double are likely to end up getting one card - the same play. It seems to me the advantage should be the same.

In this case the advantage remains the same, and your earn is exactly doubled. But in the case of a double where you MIGHT take a second hit, such as 11 vs 9, or most soft doubles, the advantage goes down by doubling, and the earn will be something less than DOUBLE.

And I did misunderstand and misquote you earlier. My apologies.

 

[psyduck]

In this case the advantage remains the same, and your earn is exactly doubled. But in the case of a double where you MIGHT take a second hit, such as 11 vs 9, or most soft doubles, the advantage goes down by doubling, and the earn will be something less than DOUBLE.

And I did misunderstand and misquote you earlier. My apologies.

Thanks for the reply and no need to apologize. Here is an example using HiLo and play 6-deck game:

advantage of double vs no double for 10 vs dealer's 9:

TC**************double************no double
-2**************10%**************10.1%
-1**************12.8%*************11.0%
0***************15.1%*************11.8%

The index for double 10 vs dealer's 9 is -1 where double shows higher advantage than no double. But where does the extra advantage come from?

PS: I had a hard time lining up the numbers with space bar.

 

[Dopple]

Isn't it just a matter of semantics. Your winnings should be directly correlated to your advantage. I sense your frustration and wish I could help.

 

[Sucker]

Yes, it IS a matter of semantics. And, like Dopple; I also wish that I had the magic words to explain this more clearly.

I believe that the person who wrote your program may have confused the word "advantage" with "expectation". This is a rather common mistake.

TC**************double************no double
-2**************10%**************10.1%
-1**************12.8%*************11.0%
0***************15.1%*************11.8%

This chart shows EXPECTATION.

In the third column, the advantage IS equal to the expectation, but in the second column, the advantage is only 1/2 of expectation.

 

[Canceler]

PS: I had a hard time lining up the numbers with space bar.

You can use the code button (#) to keep your columns straight.

TC            double            no double
-2             10%               10.1%
-1             12.8%             11.0%
 0             15.1%             11.8%

 

[iCountNTrack]

Psyduck,

I think you are confusing the initial bet advantage(IBA) commonly known as EV, with the total bet advantage. When calculating the initial bet advantage the extra wager used for a double or split is not incorporated in the calculation. IBA is always used to determine the optimum playing decision.
For hands such as 11vs6 where you are only going to take one card regardless of whether you hit or double your hand, the IBA for doubling is twice the IBA for hitting (for a full or infinite deck).
For hands such as 11 Vs 9 the IBA for doubling (for a full or infinite deck) is reduced(not twice the IBA for hitting) because we are giving up taking another hit card if needed.

 

[London Colin]

For hands such as 11 Vs 9 the IBA for doubling (for a full or infinite deck) is reduced because we are giving taking another hit card if needed.

To be consistent with the terminology, shouldn't that read 'the total bet advantage is reduced'?