Not doubling against dealer 2,3,4 at high count.

UK-21

UK-21

Well-Known Member
Some while back I posted that in order to reduce variance, and the risk of having to go home early having lost my entire session pot, I didn't double down against a dealer 2,3 or 4 at high counts where I had a "big" bet out. I was pelted with electronic rotten fruit for even suggesting such a thing.

As a result of a PM exchange with Flash, I've made an attempt to calculate roughly what the cost/loss in profit is for doing this, and whether in fact I am tossing a big chunk of my EV down the pan as others have suggested. Before discussing the numbers though, I'll reiterate that I'm not a particular maths head and don't want to turn this into an exercise in getting stuck into a heavy round of statistical analysis. Also, I play for recreation only at low stakes, don't play with a fixed bankroll and usually visit the house of chance with around 40-50 units in the knowledge that on occassions I will lose the lot (although it hasn't happened yet).

I've attached a spreadsheet with some numbers on it that anyone is free to peruse and I'll appreciate any comments that help me fine tune the figures. I've done three calcs, all pretty rudimentary and with the aim of pointing me in the right direction rather than providing a precise answer. I don't have a sim which would have been the simple answer - run a billion hands for applying and not applying these plays and take the overall win amount one from t'other to arrive at a pretty accurate figure for the loss in profit. All three calcs have been based on the frequency that these plays are likely to be made (taken from Don Schlesingers Blackjack Attack) and multiplied by the frequency of TCs +3, +4 and +5+ - they add up to almost 8% so I'm satisfied these are in the right area.

Method one.
Simply calculated the frequency that these hands will come up, and multiplied these by the betting unit, unit value and approximate %age advantage at each true count. Calculated the difference in profit from hitting and doubling down and took this as the cost of applying these plays. Divided by 70 to get the approx cost per hour etc.

Method two.
Used the cost of play chart for OTT 6 deck game (one we have here in the UK) that BS is based upon to determine the profit/loss difference between doubling down and hitting for each play. I've adjusted these figures by multiplying them by 1.15, 1.20 and 1.25 for TCs +3, +4 and +5+ respectively as a weighting to allow for the plus TCs - this opens up the gap between the hit and double down cost to give an increase to reflect the better long term returns of DD over H. 9v2 shows as a neg figure as OTT BS says hitting has a better return than doubling down, but the effect is pretty insignificant, so I've left it in for consistency.

Again, I've tallied the total loss in profit and divided this by 70 hands per hour to arrive at a cost per hour of adopting this strategy.

Method three.
Based on the fingers in the table in Blackjack Attack that shows the long term cost in cents per $100 bet for deviating from BS, I have calculated the loss in profit on these plays and again calculated the cost per hour. I don't know how DS calculated these figures, or what deviating from BS refers to; ie not doubling down but hitting or not doubling down but standing - for this exercise I've assumed the former.

I appreciate that none of the calcs above will provide a definitive answer on which to bet my pension, but the worst case scenario amongst the three (method 2) indicates that the longer term costs of not doubling against a dealer 2,3,4 at TC+3 or higher is less than £1 an hour, based on 70 hands an hour. Bearing in mind the number of units I have at my disposal when I play, this seems a reasonable cost to swallow to reduce the risk of not tapping out and having to make the 50 mile drive home shortly after arriving at the felt. Like everyone else, my biggest losses have been at high counts.

Again this is about risk and return. I found an article authored by James Grosdean and Prevan Mankodi at BJMaths.com that looks at something similar - when does the return not outweigh the risk of making certain plays or betting certain levels? It is pretty heavyweight on the maths though and aims to explain the optimum bet levels for certain plays.

Thanks in advance to everyone who sits down with a cup of coffee and reviews the numbers.
 

Attachments

UK-21

UK-21

Well-Known Member
OTT - "Off the top". The first hand of a newly shuffled deck/shoe. In theory, basic strategy is only valid for the first hand, and after that there will be minute composition changes to take account of, although of course we don't worry about such changes in practice.
 
psyduck

psyduck

Well-Known Member
I say if you hesitate to double with your "max" bet out, then your max is too big for you!
 
UK-21

UK-21

Well-Known Member
Not quite, more a case of if the doubling a max bet risks a hefty proportion of the chips that are sitting in front of me at any one time. Would you, for example, double A4v4 at TC+5 with a max bet out, knowing that the DD return is only marginally better than hitting, if it meant that you would lose all for the session if you didn't win or push the hand?
 
B

bj21abc

Well-Known Member
Looks like you are talking about Risk-Averse indices - which as I understand maximize SCORE rather than EV - for example if you were to double A8 vs 5 on TC=+1 you would be maximizing EV, but increasing variance - and risk - so that your SCORE would be higher if you doubled only at +2.

However risk-averse indices are usually only ~ 1 or maybe 2 numbers off the regular indices, and what you are describing is a complete departure.

Couple of questions:

1. Your session BR is 40-50 units - so when you say "Would you, for example, double A4v4 at TC+5 with a max bet out, knowing that the DD return is only marginally better than hitting, if it meant that you would lose all for the session if you didn't win or push the hand?" you mean when you are down to your last 2 big bets ?

2. What would you do in the same situation (TC=max bet) if you were dealt 8-8 vs 6, then a 3 on each 8 ? Would you not double as your session BR was exhausted ?

3. What is your max bet ? It sounds like your session BR is quite small - what is the logic behind a session BR if home is an hour away ? Is it mainly to avoid a single-session loss that would make your play unrecreational ?

I guess you're saying that you play for fun and would like to know how much money this strategy change would cost you, a price you're probably prepared to pay to keep variance down.

SO perhaps a good question to ask would be "what strategy changes can I make for a maximum reduction in variance with minimum cost of EV" ? I guess all splits and doubles would be candidates here, as well as insurance.

As I have forked out my $80 for CVdata :) I will try to run some sims when I get back to my desktop

D.
 
creeping panther

creeping panther

Banned
newb

newb99 said:
Some while back I posted that in order to reduce variance, and the risk of having to go home early having lost my entire session pot, I didn't double down against a dealer 2,3 or 4 at high counts where I had a "big" bet out. I was pelted with electronic rotten fruit for even suggesting such a thing.

As a result of a PM exchange with Flash, I've made an attempt to calculate roughly what the cost/loss in profit is for doing this, and whether in fact I am tossing a big chunk of my EV down the pan as others have suggested. Before discussing the numbers though, I'll reiterate that I'm not a particular maths head and don't want to turn this into an exercise in getting stuck into a heavy round of statistical analysis. Also, I play for recreation only at low stakes, don't play with a fixed bankroll and usually visit the house of chance with around 40-50 units in the knowledge that on occassions I will lose the lot (although it hasn't happened yet).

I've attached a spreadsheet with some numbers on it that anyone is free to peruse and I'll appreciate any comments that help me fine tune the figures. I've done three calcs, all pretty rudimentary and with the aim of pointing me in the right direction rather than providing a precise answer. I don't have a sim which would have been the simple answer - run a billion hands for applying and not applying these plays and take the overall win amount one from t'other to arrive at a pretty accurate figure for the loss in profit. All three calcs have been based on the frequency that these plays are likely to be made (taken from Don Schlesingers Blackjack Attack) and multiplied by the frequency of TCs +3, +4 and +5+ - they add up to almost 8% so I'm satisfied these are in the right area.

Method one.
Simply calculated the frequency that these hands will come up, and multiplied these by the betting unit, unit value and approximate %age advantage at each true count. Calculated the difference in profit from hitting and doubling down and took this as the cost of applying these plays. Divided by 70 to get the approx cost per hour etc.

Method two.
Used the cost of play chart for OTT 6 deck game (one we have here in the UK) that BS is based upon to determine the profit/loss difference between doubling down and hitting for each play. I've adjusted these figures by multiplying them by 1.15, 1.20 and 1.25 for TCs +3, +4 and +5+ respectively as a weighting to allow for the plus TCs - this opens up the gap between the hit and double down cost to give an increase to reflect the better long term returns of DD over H. 9v2 shows as a neg figure as OTT BS says hitting has a better return than doubling down, but the effect is pretty insignificant, so I've left it in for consistency.

Again, I've tallied the total loss in profit and divided this by 70 hands per hour to arrive at a cost per hour of adopting this strategy.

Method three.
Based on the fingers in the table in Blackjack Attack that shows the long term cost in cents per $100 bet for deviating from BS, I have calculated the loss in profit on these plays and again calculated the cost per hour. I don't know how DS calculated these figures, or what deviating from BS refers to; ie not doubling down but hitting or not doubling down but standing - for this exercise I've assumed the former.

I appreciate that none of the calcs above will provide a definitive answer on which to bet my pension, but the worst case scenario amongst the three (method 2) indicates that the longer term costs of not doubling against a dealer 2,3,4 at TC+3 or higher is less than £1 an hour, based on 70 hands an hour. Bearing in mind the number of units I have at my disposal when I play, this seems a reasonable cost to swallow to reduce the risk of not tapping out and having to make the 50 mile drive home shortly after arriving at the felt. Like everyone else, my biggest losses have been at high counts.

Again this is about risk and return. I found an article authored by James Grosdean and Prevan Mankodi at BJMaths.com that looks at something similar - when does the return not outweigh the risk of making certain plays or betting certain levels? It is pretty heavyweight on the maths though and aims to explain the optimum bet levels for certain plays.

Thanks in advance to everyone who sits down with a cup of coffee and reviews the numbers.
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I for one would not be jumping all over you. I think I know what you are getting at. If you want to play risk averse, and there really is nothing wrong with that, move your indices up for doubling and take a good think on some splits, usually splits can turn a session around faster than a double.

You must have an accurate count and be a student of the F.A. theory to really make this work. IMHO. I for one. however, would never hesitate to double against that 2-3-4 you mention, at the right time.

CP
 
UK-21

UK-21

Well-Known Member
Thanks gents.

It's not so much about risk adverse indices in my case, but risk adverse betting.

In BJ we do the sums, develop our own particular strategies for the games we play, and then apply them in a disciplined but perhaps inflexible way. But, if you're like me, and play with a fixed session role (when it's gone it's gone - head to the car park) perhaps an approach like poker should be adopted. Some plays should not be automatic but mindful of how big the stack is that is sitting in front of us. So if you're up a bundle when catching 9v3 with the TC at +3 double down. If not, and losing this double would eat up a large chunk of what you have left, perhaps hitting it is a better option?

From the figures to fall out of the second set of calcs, it would seem half the loss in profits is down to not doubling 11v2,3,4 and the other half for not doubling your 9,10 and soft hands. Perhaps the answer would be a compromise on what I've proposed - double down on 11vx where there are fair odds a ten will put an appearance in as with 21 you can't lose only push. But at the other end of the scale, doubling your 9 against a dealer 2 leaves too much room for the dealer to make 20 or 21 as a result of the (unknown) 7,8,9 plus 10/A effect.

If you accept the figures to drop out of the bottom are in the right area, then not doubling against a 2,3,4 at TC+3 or more would seem to reduce the EV by around 15%. But if doing so increases the variance by 15%+, for a risk adverse recreational player (in contrast to an AP looking to maximise EV) perhaps this is a fair trade off?

In the example given (8,8v6), I'd dig deep and cover the doubles after splitting them as the odds are it'll be a win or push over the two hands, and with a pretty fair chance of recovering the losses sustained to that point.
 
StandardDeviant

StandardDeviant

Well-Known Member
Great Question!

This is quite interesting. I have normally thought about AP as maximizing earnings subject to a given ROR. But...it is equally valid to ask the question of how to maximize earnings subject to a given bankroll volatility over time. This is a common concept in securities trading, where individuals frequently give up a (small) portion of return to avoid wild fluctuations in bankroll (and the associated ulcers). Might the same apply to our advantage play?

newb99 is on to something I think. I'm about to head off to work so I can't think deeply about this now, but I did take a quick look at the tables in Appendix A of BJA. For example, Table A52 on page 445, which shows EV for 6D S17: Dealer's Upcard 3. For A,6 v. 3 there are the following EVs:

Stand=-0.113384
Hit=0.030062
Double=0.057996

So hitting instead of doubling gives up ~0.028 EV (a 48% reduction in EV) for the "benefit" of cutting variation from that play in half. Mightn't a player who wants to reduce variation make a few of these plays to smooth out her bankroll curve, while still maintaining an overall positive expectation?

Plays like this would also provide the benefit of some camo.
 
QFIT

QFIT

Well-Known Member
The purpose of RA indexes is to increase EV with no increase in risk. But, if you simply start making strategy changes to reduce doubling and splitting, this will reduce EV. And if you reduce EV, overall risk will increase. If you are concerned about adding to your initial bet, the solution is to reduce the initial bet (i.e. reduce your unit size), not mess up your strategy.
 
UK-21

UK-21

Well-Known Member
StandardDeviant said:
This is quite interesting. I have normally thought about AP as maximizing earnings subject to a given ROR. But...it is equally valid to ask the question of how to maximize earnings subject to a given bankroll volatility over time. This is a common concept in securities trading, where individuals frequently give up a (small) portion of return to avoid wild fluctuations in bankroll (and the associated ulcers). Might the same apply to our advantage play?

newb99 is on to something I think. I'm about to head off to work so I can't think deeply about this now, but I did take a quick look at the tables in Appendix A of BJA. For example, Table A52 on page 445, which shows EV for 6D S17: Dealer's Upcard 3. For A,6 v. 3 there are the following EVs:

Stand=-0.113384
Hit=0.030062
Double=0.057996

So hitting instead of doubling gives up ~0.028 EV (a 48% reduction in EV) for the "benefit" of cutting variation from that play in half. Mightn't a player who wants to reduce variation make a few of these plays to smooth out her bankroll curve, while still maintaining an overall positive expectation?




Plays like this would also provide the benefit of some camo.
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Remember I'm only proposing this at TCs of +3 and higher (8%ish of the time), to reduce the variance in losing with big and max bets out.
 
B

bj21abc

Well-Known Member
For low-stakes play, reducing unit size may not be an option (the friendly local store may not accept $4 bets)

QFIT said:
The purpose of RA indexes is to increase EV with no increase in risk. But, if you simply start making strategy changes to reduce doubling and splitting, this will reduce EV. And if you reduce EV, overall risk will increase. If you are concerned about adding to your initial bet, the solution is to reduce the initial bet (i.e. reduce your unit size), not mess up your strategy.
Click to expand...
 
UK-21

UK-21

Well-Known Member
There is of course the table min impact, which combined with the problems of busy tables and no opportunities for the wonging in/out thing will result in a greater amount being wagered when there is no advantage at zero and negative counts. Also, there will be around 16%ish of the time when you'd be playing with a smaller advantage and would make these plays, but with a smaller bet out - so reducing the unit value would mean an even greater reduction in $/£s, but with a higher degree of win/loss variance perhaps?
 
moo321

moo321

Well-Known Member
Why the **** are we even talking about this?! Are you guys completely insane? I get a boner just thinking about doubling down with a max bet against a low card.

Bottom line: under no circumstances should you place a bet so high that you would be unwilling to double down against a 10, muchless a 2-4.

For ****'s sake, learn some risk averse indices, use a smaller unit, or back-count if you want to reduce your variance.
 
B

bjcount

Well-Known Member
moo321 said:
Why the **** are we even talking about this?! Are you guys completely insane? I get a boner just thinking about doubling down with a max bet against a low card.

Bottom line: under no circumstances should you place a bet so high that you would be unwilling to double down against a 10, muchless a 2-4.

For ****'s sake, learn some risk averse indices, use a smaller unit, or back-count if you want to reduce your variance.
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Moo321,

Your my HERO :grin:

BJC
 
C

chevelless

New Member
I just recently bought a DVD for training from a long time blackjack pro . It is long and sometimes a little out there but overall the content is very good if you are truly interested in learning how to count and what the cards really mean as they roll out of the deck. Check out this site : captainblackjack.com . good luck to all , ChevelleSS
 
UK-21

UK-21

Well-Known Member
moo321 said:
Why the **** are we even talking about this?! . . .
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Well . . . . it started with me trying to come up with some figures on what the impact of doing this is. The impact cost if you like. The same as the impact cost of cover plays - wouldn't you want to know the effect of deliberately deviating from BS for whatever reason?

There're many postings on this site surrounding losing bundles despite the high count, and I suspect that the majority of those high count big losses are the result of doubling down against a dealer 2,3,4 - I may be wrong.

For info, in the UK doubling down against a dealer 10 is not a BS play and carries a health warning. And in general, back-counting and wonging in isn't an option due to the fact that at most times tables will be busy, and when they're not you'll stick out like a pair of bulldog's if you do it three or four times (most UK casinos I've visited you can stand on one side and see the other quite clearly - no super Vegas style places here).

So there it is . . . just examining an option for those of us looking to round off the sharp variance edges. If the variance ain't a problem, then it ain't a problem!
 
moo321

moo321

Well-Known Member
newb99 said:
Well . . . . it started with me trying to come up with some figures on what the impact of doing this is. The impact cost if you like. The same as the impact cost of cover plays - wouldn't you want to know the effect of deliberately deviating from BS for whatever reason?

There're many postings on this site surrounding losing bundles despite the high count, and I suspect that the majority of those high count big losses are the result of doubling down against a dealer 2,3,4 - I may be wrong.

For info, in the UK doubling down against a dealer 10 is not a BS play and carries a health warning. And in general, back-counting and wonging in isn't an option due to the fact that at most times tables will be busy, and when they're not you'll stick out like a pair of bulldog's if you do it three or four times (most UK casinos I've visited you can stand on one side and see the other quite clearly - no super Vegas style places here).

So there it is . . . just examining an option for those of us looking to round off the sharp variance edges. If the variance ain't a problem, then it ain't a problem!
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I don't use cover plays, because it's a ridiculous cost to pay for straight counting. We're talking about maybe a 2% edge, and you're willing to give some of that up just to reassure yourself that you might get to play longer? Just get the money and get out. If you get caught, move on.

As far as cover or variance reducing plays go, this is one of the worst ideas I can think of. You're probably giving up a day's EV by not doubling down a max bet against a 4. It simply should never be done. Period.
 
UK-21

UK-21

Well-Known Member
moo321 said:
. . . You're probably giving up a day's EV by not doubling down a max bet against a 4. It simply should never be done. Period.
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Can you quantify that statement with some numbers and the basis for your assumptions please? That's what I was looking for with my original post. I've done some calcs that indicate the loss in EV is nowhere near as high as you suggest, although I'll admit they're rudimentary and need fine tuning at the very least. I do have an open mind on it.
 
moo321

moo321

Well-Known Member
newb99 said:
Can you quantify that statement with some numbers and the basis for your assumptions please? That's what I was looking for with my original post. I've done some calcs that indicate the loss in EV is nowhere near as high as you suggest, although I'll admit they're rudimentary and need fine tuning at the very least. I do have an open mind on it.
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Well, according to the wizardofodds, the EV of doubling 11 v. 4 is 56.6%. That's a assuming a neutral count, which it's not if you have a max bet out.

So, let's say 20 units doubled is 40 units*.56 = 22.4 units

22.4 units is a nice days work. I'm doubling down whenever I have 11 v. 4 with a max bet out.
 
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