Back Bettors (Part 2): How to fully exploit defensive splits

[Cacarulo]

Hi everyone,

After reviewing DogHand's valuable study, I’ve decided to contribute some ideas, with a focus more towards card counters.

The first thing to keep in mind is that there are two types of splits: offensive and defensive. Offensive splits are those with a
positive expected value, while defensive splits have a negative expected value.

For this analysis, let’s assume that you can’t split for less and that the BB (Back Bettor) is not part of a team with the FB (Front Bettor),
although he could be. We’ll also assume we are playing in a casino where back bets are allowed and, most importantly,
we are not required to follow the FB’s decisions.

As I mentioned at the beginning, this is just a contribution to convey the idea, not a complete strategy. For the sake of the example,
I will use Hi-Lo with standard American rules: 6D, S17, DOA, DAS, SPA1, SPL3, NS.

What is this analysis about? If the split is offensive, the BB will follow the FB in all bets. However, if the split is defensive,
the BB will only follow the first hand.

The key question is: Is there a TC where a defensive split becomes an offensive split? The answer is YES.

Here are some examples:

a) 22 vs 2 becomes offensive at a TC >= +5
b) 22 vs 3 becomes offensive at a TC >= +1
c) 33 vs 2 becomes offensive at a TC >= +7
d) 33 vs 3 becomes offensive at a TC >= +2

This shows that if the BB is counting from behind and knows these indices, he could follow the FB fully in many
splits that initially appeared defensive.

Of course, all defensive splits could be explored, but that’s beyond the scope of this post.

Sincerely,
Cac

[Mirana]

That is a very interesting idea, thank you for sharing! Do you have results for every other split?
Do we need the assumption that the BB is not part of a team with the FB? I think it doesn´t make a difference for this analysis, whether they are a team or not. If they are a team the FB makes just makes more splits to save some hands of the BB.
Btw: I´m still looking for the study of dog hand

[DSchles]

That is a very interesting idea, thank you for sharing! Do you have results for every other split?

Perfect question for Gronbog's graphs: every edge of every hand at every (reasonable) TC. Just look for when the EV crosses over from negative to positive.

Don

[Cacarulo]

That is a very interesting idea, thank you for sharing! Do you have results for every other split?
Do we need the assumption that the BB is not part of a team with the FB? I think it doesn´t make a difference for this analysis, whether they are a team or not. If they are a team the FB makes just makes more splits to save some hands of the BB.
Btw: I´m still looking for the study of dog hand

You're welcome. No, I haven’t analyzed each of the splits, but what Don suggests regarding Gronbog’s charts is the perfect answer.
We can not only analyze defensive and offensive splits, but we can also analyze defensive and offensive double downs.
Furthermore, we can calculate the index at which a split or a DD transitions from defensive to offensive, and vice versa!

Sincerely,
Cac

[aceside]

This is the first time I’ve ever heard of this term “defensive double downs.” Is there an example of such a situation?

[Seraph]

Thanks for the contribution Cac

[James989]

Hi everyone,

After reviewing DogHand's valuable study, I’ve decided to contribute some ideas, with a focus more towards card counters.

The first thing to keep in mind is that there are two types of splits: offensive and defensive. Offensive splits are those with a
positive expected value, while defensive splits have a negative expected value.

For this analysis, let’s assume that you can’t split for less and that the BB (Back Bettor) is not part of a team with the FB (Front Bettor),
although he could be. We’ll also assume we are playing in a casino where back bets are allowed and, most importantly,
we are not required to follow the FB’s decisions.

As I mentioned at the beginning, this is just a contribution to convey the idea, not a complete strategy. For the sake of the example,
I will use Hi-Lo with standard American rules: 6D, S17, DOA, DAS, SPA1, SPL3, NS.

What is this analysis about? If the split is offensive, the BB will follow the FB in all bets. However, if the split is defensive,
the BB will only follow the first hand.

The key question is: Is there a TC where a defensive split becomes an offensive split? The answer is YES.

Here are some examples:

a) 22 vs 2 becomes offensive at a TC >= +5
b) 22 vs 3 becomes offensive at a TC >= +1
c) 33 vs 2 becomes offensive at a TC >= +7
d) 33 vs 3 becomes offensive at a TC >= +2

This shows that if the BB is counting from behind and knows these indices, he could follow the FB fully in many
splits that initially appeared defensive.

Of course, all defensive splits could be explored, but that’s beyond the scope of this post.

Sincerely,
Cac

I've thought about this before, the problem is, if the front bettor not your team member, you can't fully utilise the complete RIDER STRATEGY. For example, front bettor(BS player) will not split 2,2 vs 8 and you can't execute RIDER STRATEGY. However, I agree that your this defensive/offensive split may still help but the gain should much less than 0.19%(please note that, when FB/BB betsize ratio is 1 : 20, you can gain 0.19% with help of own team front bettor and complete RIDER STRATEGY).


Another problem is you have to find a front bettor who 100% know basic strategy and yet allow you to bet behind.


Am I missing something ?

[James989]

This is the first time I’ve ever heard of this term “defensive double downs.” Is there an example of such a situation?

If the count is high, and FB choose not to double down, can BB double down ?

For example, (4,5) vs 2, TC = +1, FB is BS player, choose to HIT, so can BB double down ?

[aceside]

No, back better does not have any say to strategic decisions.

[Mirana]

If the count is high, and FB choose not to double down, can BB double down ?

For example, (4,5) vs 2, TC = +1, FB is BS player, choose to HIT, so can BB double down ?

That is not possible, because FB might demand another card after hitting. BB can´t double down, if FB doesn´t.

You're welcome. No, I haven’t analyzed each of the splits, but what Don suggests regarding Gronbog’s charts is the perfect answer.
We can not only analyze defensive and offensive splits, but we can also analyze defensive and offensive double downs.
Furthermore, we can calculate the index at which a split or a DD transitions from defensive to offensive, and vice versa!

Sincerely,
Cac

As a new member I`m careful about contradicting blackjack authorities like Cacarulo, but I don´t think there are any defenisve double downs. As far as I know the EV is always positive, if we double down (therefore the strategy for doubling down is the same for FB and for BB, see Wong, Professional Blackjack, p. 95ff.). Please explain, if you meant it differently.

[James989]

No, back better does not have any say to strategic decisions.

Then how BB apply defensive/offensive double down strategy ? FB double down(follow BS) and BB choose not to double down when TC = -ve ?

[21forme]

My only experience with back betting was at Foxwoods. The player in the chair makes all strategic decisions. However, the back bettor could independently take INS and play only one of two hands on a split.

I suspect aceside is talking out of his ass (as usual) with no personal back betting experience.

[James989]

My only experience with back betting was at Foxwoods. The player in the chair makes all strategic decisions. However, the back bettor could independently take INS and play only one of two hands on a split.

I suspect aceside is talking out of his ass (as usual) with no personal back betting experience.

My opinion :-

SPLIT - BB can apply offensive strategy for about 10 hand combinations( 22 vs 2, 22 vs 3, . . . .66 vs 2 . . .33 vs 7 and 77 vs 7). There may be some gains.
DOUBLE DOWN - BB can apply defensive strategy (BB not to double down when the count is low).

However, if FB is not a team member, BB can't use rider strategy to split hands such as 22 vs 8, 22 vs 9 . . . .77 vs 8 . . . . .This is the disadvantage.