Two Unrelated Questions

[CanKen]

1) An unusual situation, at least for me. I'm sitting next to a good, BS, non-counting player. He's betting quite a bit more than I am but not doing too well. On this hand he gets A,7 vs 4, but hasn't enough money to double, so he asks me if I want the double-down action. The count is quite good, and I happily accept and match his bet. We win the hand and I thank him for the opportunity.
But thinking about it after, I wonder, since his bet was about twice my, (correct for me), bet that round, maybe I should have doubled for less, just matching my own bet size, not his? Comments?

2) If only one spot is available, I spread 1-14, but if two spots are open I spread 1x1-2x10. What one spot spread is this equivalent to? I have been told that it's not equivalent to 1-20.

 

[gorilla player]

some answers

Others can probably answer better, but this will get you to thinking.

1. Your bet size is probably tailored to your bankroll and acceptable ROR? Obviously if you matched his larger bet for the DD play, you just bet more than normal. And increased your ROR somewhat (probably not a lot unless his bet was _way_ bigger than yours. IE even with a good count, you don't win all double downs...

2. 2x10 is definitely not the same as 1-20. For a guess, I would say it is more like 1-16, but someone here probably knows exactly how to calculate this. I'm just a computer guy.

 

[Automatic Monkey]

How I calculate it

The proper bet for a situation is related to your advantage and your standard deviation. Now for certain DD hands your advantage is very high, so proportianally the appropriate maximum bet is very high. For DD hands the average advantage is somewhere around 15-20%. Let's say I had an opportunity to DD on someone's 11 against a dealer 6. I'd feel very comfortable betting 10% of my bankroll in that situation. A7 vs. 4 is not quite as good, but still your advantage is quite a bit higher than it normally would be just based on the count. So I think you did the right thing.

Spreading to multiple hands definitely decreases your variance to where you can increase your total bet with the same risk. It's a very profitable thing to do. This probably isn't totally accurate, but I multiply the bet I would use on 1 hand by the square root of 2 or 3 hands when playing multiple hands. E.g., if the bet would be $100 on 1 hand, I'd split $140 among 2 hands or $170 across 3 hands.

 

[CanKen]

Re: Answers

1. Your bet size is probably tailored to your bankroll and acceptable ROR? Obviously if you matched his larger bet for the DD play, you just bet more than normal. And increased your ROR somewhat (probably not a lot unless his bet was _way_ bigger than yours. IE even with a good count, you don't win all double downs...

Right - I set my bets at about 2/3 Kelly, which makes my max bet about 1% of BR.
This gives a pretty conservative ROR, so, as you say, the play in question was an overbet, but nothing to worry about.

2. 2x10 is definitely not the same as 1-20. For a guess, I would say it is more like 1-16, but someone here probably knows exactly how to calculate this. I'm just a computer guy.

If anyone can supply the math to calculate this I would appreciate it.

 

[CanKen]

Thanks for the input

The proper bet for a situation is related to your advantage and your standard deviation. Now for certain DD hands your advantage is very high, so proportianally the appropriate maximum bet is very high. For DD hands the average advantage is somewhere around 15-20%. Let's say I had an opportunity to DD on someone's 11 against a dealer 6. I'd feel very comfortable betting 10% of my bankroll in that situation. A7 vs. 4 is not quite as good, but still your advantage is quite a bit higher than it normally would be just based on the count. So I think you did the right thing.

Makes sense. If you knew ahead of time that you were going to get a good DD on a hand, you could put out a bigger than normal bet.

Spreading to multiple hands definitely decreases your variance to where you can increase your total bet with the same risk. It's a very profitable thing to do. This probably isn't totally accurate, but I multiply the bet I would use on 1 hand by the square root of 2 or 3 hands when playing multiple hands. E.g., if the bet would be $100 on 1 hand, I'd split $140 among 2 hands or $170 across 3 hands.

I understand what you are saying. For two hands, I use 75% of the one hand bet on each, (or a little less), which amounts to about the same as what you said. I've never used three spots.
However, this isn't quite what I was asking. What I'd like to know is what single hand spread would be equivalent to a 1x1 to 2x10 spread. Apparently it's not the same as 1-20?

 

[Dog Hand]

Equivalent to 2x10...

CanKen,

From your post:

E.g., if the bet would be $100 on 1 hand, I'd split $140 among 2 hands or $170 across 3 hands.

I understand what you are saying. For two hands, I use 75% of the one hand bet on each, (or a little less), which amounts to about the same as what you said. I've never used three spots.
However, this isn't quite what I was asking. What I'd like to know is what single hand spread would be equivalent to a 1x1 to 2x10 spread. Apparently it's not the same as 1-20?

So you're spreading a total of 20 over two hands. According to the above, that's equivalent to betting
(20)*($100/$140) = 14.28571... on one hand. Round it off and say that 1x1 to 2x10 is roughly equivalent to one hand with a 1-14 spread.

Dog Hand