Confusing Index Plays

2

21Menace

Well-Known Member
#1
#1
I learned the illustrious 18 a couple months ago but never realized that a couple make no sense to me. If it matters, I play 6deck, H17, das, and use hi/low.

First, the index for 11vsA is +1, meaning double at +1 and above. So why does bs say to double? You'd think it would say hit if thats the correct play with a 0 count.

Second, the index for 10vs10 is 4. As the count goes up you have a greater chance of getting a high card to make a good hand with your starting 10, but the dealer's odds of having a 10 underneath go up just as much right? So why risk double the money when you gained no advantage from a higher count?

I'm sure I'm just missing something from both of them. A while ago I was confused about the index for 16v10 being 0 and I got some really good explanations. So I'm hoping you guys will have some for me here!
 
SleightOfHand

SleightOfHand

Well-Known Member
#2
#2
21Menace said:
I learned the illustrious 18 a couple months ago but never realized that a couple make no sense to me. If it matters, I play 6deck, H17, das, and use hi/low.

First, the index for 11vsA is +1, meaning double at +1 and above. So why does bs say to double? You'd think it would say hit if thats the correct play with a 0 count.

Second, the index for 10vs10 is 4. As the count goes up you have a greater chance of getting a high card to make a good hand with your starting 10, but the dealer's odds of having a 10 underneath go up just as much right? So why risk double the money when you gained no advantage from a higher count?

I'm sure I'm just missing something from both of them. A while ago I was confused about the index for 16v10 being 0 and I got some really good explanations. So I'm hoping you guys will have some for me here!
Click to expand...
For the 11vA, you are probably looking at a H17 BS chart while the index of +1 is for a S17 game. BS 11vA is to hit for a S17 game.

As for doubling 10vX, its because we know that the dealer doesn't have blackjack. A 10 will help him as much as us, but an ace will not help the dealer (much).
 
D

Dopple

Well-Known Member
#3
#3
SleightOfHand said:
For the 11vA, you are probably looking at a H17 BS chart while the index of +1 is for a S17 game. BS 11vA is to hit for a S17 game.

As for doubling 10vX, its because we know that the dealer doesn't have blackjack. A 10 will help him as much as us, but an ace will not help the dealer (much).
Click to expand...
It also might be that if we get a 5 or 6 we can not hit but the dealer must.
 
Lonesome Gambler

Lonesome Gambler

Well-Known Member
#6
#6
I got mine from Exhibit CAA, but CVBJ will work, and I believe even the latest edition of Professional Blackjack has them. I use what I hypothesize are the top-50 indices (I'm slightly clueless at running CVData), so if you need any particular ones, I can probably tell you.
 
2

21gunsalute

Well-Known Member
#7
#7
Lonesome Gambler said:
I got mine from Exhibit CAA, but CVBJ will work, and I believe even the latest edition of Professional Blackjack has them. I use what I hypothesize are the top-50 indices (I'm slightly clueless at running CVData), so if you need any particular ones, I can probably tell you.
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Do they vary much from S17?
 
M

Meistro

Well-Known Member
#8
#8
I hope not :)

Index plays for 6 deck H17, DAS, DA2, NS

16 vs 10 is the same, 0

15 vs 10 is the same, 4

16 vs 9 is the same. 5

Insurance is the same. 3

12 is different! 12 vs 2 is 3, 12 vs 3 is 1, 12 vs 5 is -2 and 12 vs 6 is -4

TT vs 5 and 6 are the same -5 and -4 respectively.

99 vs A is +2 instead of +3

9 vs 7 and 2 are the same - 3 and 1

13 is different, 13 vs 2 is -1 and 13 vs 3 is -3
 
2

21Menace

Well-Known Member
#9
#9
SleightOfHand said:
For the 11vA, you are probably looking at a H17 BS chart while the index of +1 is for a S17 game. BS 11vA is to hit for a S17 game.

As for doubling 10vX, its because we know that the dealer doesn't have blackjack. A 10 will help him as much as us, but an ace will not help the dealer (much).
Click to expand...
Aaah got it! For some reason CVCX has 1 at the index for 11vsA even though I have H17 checked.
 
M

Meistro

Well-Known Member
#11
#11
My notation was confusing, I mean +3 and +1. Perhaps the school is using risk adverse index plays? Personally, I'm into expectation maximization.
 
Lonesome Gambler

Lonesome Gambler

Well-Known Member
#12
#12
Meistro's right on 9v7 and 3. The other difference is, of course, 11vA. Also, A8v6 is 0 in a H17 game, which is why it's basic strategy, but only in neutral or positive counts. The surrender indices are the biggest difference, but I don't have the S17 indices in front of me right now. Again, CVBJ is a good source.
 
N

Nynefingers

Well-Known Member
#14
#14
Meistro said:
My notation was confusing, I mean +3 and +1. Perhaps the school is using risk adverse index plays? Personally, I'm into expectation maximization.
Click to expand...

Why? I thought the risk averse indices were the "correct" indices in almost all cases. Don't they strike the mathematically optimal balance of risk vs. reward? In other words, if you are willing to accept the extra variance associated with maximizing the EV, can't you get a bigger increase in EV for the same increase in variance by changing other factors, such as the unit size or the spread? I realize that some of those things can't be changed on a continuous scale (unit will probably be in increments of $5 or more, for example). But unless you are in a game where you cannot play a larger unit or bigger spread, why would you prefer EV maximizing indices vs. risk averse indices? :confused:
 
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