Trying to understand why certain strategy deviations exist

[meteomonk]

Many of the deviations from basic strategy during various high or low counts make sense i.e. doubling on hard 8 vs. 5. When teaching my girlfriend basic strategy i have found it sensible to explain the reason for each decision. Now if any of you have an understanding of some of the harder to grasp deviations i would love an explanation. Sorry if this has been covered a link would be appreciated as well.

1. Stand on 16 vs. 10----obviously this is because your chance of busting becomes greater during high counts, and the dealer will bust more frequently than you would win hitting the hand. Yet I find it very strange that the count required to stand on 16 vs. 7 is significantly higher. The only possible reason is that the dealer busts more frequently with a 10 up than 7 during fairly high counts. but this seems to defy logic as the only cards that would allow the dealer to NOT draw again with a 7 are Tens or an Ace. any explanation?

2. Double 10 vs. 10. I always feel sketchy about it yet it seems to work quite well. IF you have a better chance of recieving a 10 that means there are good odds of the dealer having a 10 underneath. oh i just thought of this, Perhaps this has to do with the dealer not having a blackjack and you hoping for an ace some of the time?

I suppose these arn't deviation questions but i am curious

3. This relates to number 1. but it isn't a deviation. If the dealer does in fact bust less on 7 than 10, why do you surrender 16 vs. 9 and 10 but not 7 until very high counts? if you will bust too frequently against a 10, why try to hit against a 7?

4. (a)Do you only take even money when the count would merit insurance?
(b)does this decision change one way for variance and one way for win rate?
(c)how would the decision change on a 6/5 payout game?

5. Also, do you guys surrender hard 17 against an ace? my bs card says to on a H17 game but it seems like you would win more than 1/3rd of the time standing.?

Thanks! So many questions! have fun answering them, I appreciate it.

 

[ihate17]

Some thoughts

Many of the deviations from basic strategy during various high or low counts make sense i.e. doubling on hard 8 vs. 5. When teaching my girlfriend basic strategy i have found it sensible to explain the reason for each decision. Now if any of you have an understanding of some of the harder to grasp deviations i would love an explanation. Sorry if this has been covered a link would be appreciated as well.

1. Stand on 16 vs. 10----obviously this is because your chance of busting becomes greater during high counts, and the dealer will bust more frequently than you would win hitting the hand. Yet I find it very strange that the count required to stand on 16 vs. 7 is significantly higher. The only possible reason is that the dealer busts more frequently with a 10 up than 7 during fairly high counts. but this seems to defy logic as the only cards that would allow the dealer to NOT draw again with a 7 are Tens or an Ace. any explanation?

That dealer with a 10, has 7 of 12 cards that will beat your 16 if you stay. The dealer with a 7 may only have 5 of 13 cards that beat your 16, but he also could have a 2,3,or 4 in the hole which can set him up for an easy win.
You need to turn your thinking around a little to understand why you hit 16 vs 7 much more often than 16 vs 10. It has little to do with the dealer busting and much more to do with what kind of hand you land up with if you do not bust. You hit 16 vs 10 and draw a 2 for 18 and you are still favored to lose that hand, but if you got the same result when the dealer has a 7 showing, you are now favored to win. If the dealer only has 17, not busting on a hit means you either push or win, you can not say that if the dealer has 20. This difference is enough to make the indice for 16 vs 7 much higher than the one for 16 vs 10.

2. Double 10 vs. 10. I always feel sketchy about it yet it seems to work quite well. IF you have a better chance of recieving a 10 that means there are good odds of the dealer having a 10 underneath. oh i just thought of this, Perhaps this has to do with the dealer not having a blackjack and you hoping for an ace some of the time?


This is a more borderline question than #1, but yes if aces did not count as 11 on your double, you would not double.

ihate17

 

[callipygian]

if any of you have an understanding of some of the harder to grasp deviations i would love an explanation ...

1. Stand on 16 vs. 10 ...

2. Double 10 vs. 10 ...

ihate17 explained these quite well.

3. This relates to number 1. but it isn't a deviation. If the dealer does in fact bust less on 7 than 10, why do you surrender 16 vs. 9 and 10 but not 7 until very high counts? if you will bust too frequently against a 10, why try to hit against a 7?

For the exact same reason as ihate17 posted for #1 - the difference is how well you fare when you DON'T bust, not when you do.

4. (a)Do you only take even money when the count would merit insurance?
(b)does this decision change one way for variance and one way for win rate?

In a nutshell, no, and yes (respectively).

If you were only concerned about EV/winrate, you'd only take even money when the count merited taking insurance. If you were only concerned about variance, you'd always take even money. Most people are concerned about both, so a combination of the two is required.

For small bankrolls relative to your bet, you not only have to wait until the count is sufficiently high, but also until the EV on the insurance bet is equal to the additional fraction of your bankroll you'd be risking. If you have a 20-unit bet out at a 2% advantage, you might not want to put an additional 10-unit bet out at a 0.5% advantage. You can use OptimalBetFraction = EV/Variance to calculate when this is a good bet for you.

(c)how would the decision change on a 6/5 payout game?

I don't play 6:5 games, but I assume that even money is not offered, as it would be an incredible deal. Even money works because if the dealer has a ten, you win your insurance bet (+2*0.5) but push your blackjack (0); if the dealer doesn't, you lose your insurance bet (-0.5) but win your blackjack (+1.5), which gives the same amount.

Now, change the blackjack payout to +1.2, and "even money" becomes +0.3 extra units if dealer doesn't have a 10 (you'd net +0.7 otherwise). I doubt the casinos would be this generous.

5. Also, do you guys surrender hard 17 against an ace? my bs card says to on a H17 game but it seems like you would win more than 1/3rd of the time standing.?

By my calculation, standing hard 17 vs. dealer A in a H17 game will win 20% of the time and lose 72% of the time.

(P.S. you only need to win >25% of the time to beat surrender)

 

[EasyRhino]

Here's my "intuition" I use to explain the deviations. Are they correct? Not sure. I don't have the precise numbers in front of me now.

1) 16v10. As IH17 says, even if you don't bust, you'll probably still lose.

2) 10v10. If you have to take two cards, you'll probably bust. Doubling down strangely protects you from that, while the dealer has to keep drawing if he gets a low hand.

3) callypigian sure gave you a bunch of numbers, there. My answer is "yes", take even money at the same count as insurance. It's close enough.

4) 17vA. You have to realize how bad a 17 is. I think it's an underdog against a dealer deuce, even. Definitely surrender, in an H17 game, if it's available.

 

[moo321]

10 vs. 10 has to do with the fact that you know the dealer doesn't have an ace underneath, while you could pull an ace on your double. It's a really close double, and if you have a max bet out, the "risk averse" play is to double at +7 or so, instead of 5.

You hit the 16 vs. 7 because you're MUCH more likely to win if you catch a card. Catch a 2 and you're way ahead. Against a 10, catch a 2 and you're still way behind.

 

[meteomonk]

I don't play 6:5 games, but I assume that even money is not offered, as it would be an incredible deal. Even money works because if the dealer has a ten, you win your insurance bet (+2*0.5) but push your blackjack (0); if the dealer doesn't, you lose your insurance bet (-0.5) but win your blackjack (+1.5), which gives the same amount.

Now, change the blackjack payout to +1.2, and "even money" becomes +0.3 extra units if dealer doesn't have a 10 (you'd net +0.7 otherwise). I doubt the casinos would be this generous.

Ahh thank you! I was having a difficult time understanding the logic in your second paragraph. But after using the percentage of non-ten cards in the deck (.6923) as the percentage of time you'd win your blackjack while NEVER taking even money and a $100 bet as reference.

With 3:2 payout and never taking even money you'd net about avg. $104
while obviously always taking even money you'd average $100

With 6:5 payout and never taking even money you'd net $83
compared again to the $100 alway taking even money


I hope my numbers are correct as you did say .7 where i got .83

Now here are my further questions........

1. is the option of even money included in the 1.39% house advantage improvement given for a 6:5 game?
2. if not, it seems like the option of even money would occur fairly rarely and not have much of an overall effect on the expectancy reduction. Any numbers on what effect this rule would have for the player?
3.just curious..what percentage of hands do blackjacks occur

I'm hoping the news is that most 6:5 games do not typically offer even money
meaning that the game i have been playing with between a 1-20 and 1-30 spread actually isn't being affected the full %1.39 by the blackjack payout.

again Do you have any guesses as to how much an even money option on 6:5 would raise your % expectency?

I can only draw a vauge guess. 1/13 of the cards are aces, and as in single deck you're blackjack contains 1/4 of the aces, aprox. 6% of the time you have a blackjack the dealer has an ace up.

You called it an "incredible deal" but i'm curious, if it only occurs 6% of the time that you get a blackjack, and increases your take .25 or something.

I don't know just a lot of curiosity, and guessing at numbers. I think I just want to make the 6:5 game work as I have gotten away with a huge bet spread and its what i learned to play on.

Thank you everyone for input!:cool2:

 

[hot dealer]

16 vs. dealer's 10

Since the early '90s I have created several blackjack programs in everything from DOS Basic to Visual Basic. At first I was simply wanting to verify that basic strategy tables were correct and later to test variance and winning rates over millions of hands with different counting methods.

One difference all of my programs had from basic strategy was showing a very slight advantage of standing on 16 vs. a dealer's 10 (even at a neutral count). You're basically gonna lose the vast majority of times with this hand regardless of what you do, but I've always stood on this hand (except at a negative count). I've always smiled when I didn't bust myself with this hand and the dealer had a small card down and pulled a big card to bust.

 

[EasyRhino]

There's an effect of removal just getting to a hard 16. The count has probalby moved (barely) negative, by virtue of the dealer having a 10, and you having whatever. That alone is enough to shift the play towards hitting being the basic strategy. That's how close it is.

As number of decks approaches infinity, the BS would be to stand, as well.

 

[Kasi]

1. is the option of even money included in the 1.39% house advantage improvement given for a 6:5 game?:

No.

 

[mdlbj]

You do not need to question this theoretically, you should do the math that tells your why. Or just play your strategy perfectly and quit whining..

 

[Kasi]

There's an effect of removal just getting to a hard 16. The count has probalby moved (barely) negative, by virtue of the dealer having a 10, and you having whatever. That alone is enough to shift the play towards hitting being the basic strategy. .

Well, yes, but then there's the efficiency of the count to identify all situations.

Like 8,6,2 vs 10 off the top of a 1-8D S17 shoe is always a hit even though like Hi-Lo for example would give a +1RC and one may think it's time to stand.

 

[EasyRhino]

Like 8,6,2 vs 10 off the top of a 1-8D S17 shoe is always a hit even though like Hi-Lo for example would give a +1RC and one may think it's time to stand.

a) Basic strategy doesn't include three-card hands, smartypants
b) 862v10 is a hit because you consumed a 6, and didn't consume a 5.
c) It doesn't matter.

 

[Kasi]

a) Basic strategy doesn't include three-card hands, smartypants

Well it does if one chooses to use a composition-dependent BS as opposed to a total-dependent BS :grin:


If a BS player is going to adopt a rule like "always stand on 3-or-more-card 16's vs 10", even though that may be a valid rule, why not take it one step further and only hit the exact 3-card hands that are called for? lol.

Other than, like you say, it really doesn't matter except you think you really know what you are doing and can feel sorry for all those ploppys who have the nerve to hit on a 10,5,A vs 10 when everyone knows it's a stand even though it has a 5 in it. :grin:

 

[bjplayer123]

At s17 game, can some one tell me whats the count for surrender hard 16 vs 7 and 8 . And no surrender game whats the count for stay 16 vs 7 and 8

Thx

 

[Meistro]

16 v 8 surrender at +4 stay at +7

16 v 7 is a stay at +9 or +10 usually (against eight, nine and ten) the surrender index is significantly lower than the stay index but I'm not aware of any surrender index for 16 v 7.

 

[bjplayer123]

16 v 8 surrender at +4 stay at +7

16 v 7 is a stay at +9 or +10 usually (against eight, nine and ten) the surrender index is significantly lower than the stay index but I'm not aware of any surrender index for 16 v 7.

Thanks alot, could you advice whats the stay index for 16 vs 8.9.10.A

 

[Meistro]

7, 5, 0, +3 (H17 only) respectively

 

[bjplayer123]

7, 5, 0, +3 (H17 only) respectively

Hi meistro

Sorry i know i asked too much, last question i promise, let say u have 3&5 vs 8 or 9 at high count, Then u hit a 7, so u have three card 15, u cant surrender after first two cards, what would you do at this point? Thanks alot man

 

[Meistro]

15 v 9 is a stay at +8
15 v 8 is a stay at +10

These are pretty unimportant indexes. It is more important to learn the hit/stand and double indexes between +1 and +6. Pair split indexes are also a low priority because they occur less frequently. It is a good idea to learn 2 or 3 new indexes every day until you have a fairly comprehensive command of most of the hi lo variations.


I'm more than happy to continue answering your questions, please do not feel like you are imposing at all. I'd also be happy to do a sweat session, where you record yourself playing through a few shoes at home and I identify any mistakes that you are making.

 

[bjplayer123]

15 v 9 is a stay at +8
15 v 8 is a stay at +10

These are pretty unimportant indexes. It is more important to learn the hit/stand and double indexes between +1 and +6. Pair split indexes are also a low priority because they occur less frequently. It is a good idea to learn 2 or 3 new indexes every day until you have a fairly comprehensive command of most of the hi lo variations.


I'm more than happy to continue answering your questions, please do not feel like you are imposing at all. I'd also be happy to do a sweat session, where you record yourself playing through a few shoes at home and I identify any mistakes that you are making.

Omg u so nice, thanks alot meistro

So at +4 or +5 when u have a 15 consist 3 or more cards vs 8 or 9 u still hit them right?