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Thread: Why A7 vs A at TC>1 become stand in S17

  1. #1


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    Why A7 vs A at TC>1 become stand in S17

    I see from Stanford Wong at in S17 game for A7 (soft 18) vs A, at TC above +1 the strategy becomes stand instead of hit. I checked with Wizard in the calculator by reducing the number of low cards outstanding, the strategy really changes from hit to stand.

    Basically, I do not understand the logic. Soft 18 vs 9, Ten, the reason why hitting is optimal is the likelihood of getting small cards like 2 or 3 while getting the picture neither hurts or help. The ace slightly helps. But with the ace, hitting soft 18 in high count is more likely to catch the picture or the ace to soft 19, so it is likely hitting does not really hurt. The 6? It helps as more 6s cause the dealer to stand on 17 more often but on the other hand the player does not like the 6 after a hit as well to hard 14. Moreover, high count also suggests 6s are depleting too. If the dealer gets a BJ, both result in a loss anyway. Why the strategy becomes stand then?

    Many thanks
    Last edited by PromVRT; 05-26-2020 at 04:03 PM.

  2. #2


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    Quote Originally Posted by PromVRT View Post
    I see from Stanford Wong at in S17 game for A7 (soft 18) vs A, at TC above +1 the strategy becomes stand instead of hit. I checked with Wizard in the calculator by reducing the number of low cards outstanding, the strategy really changes from hit to stand.

    Basically, I do not understand the logic. Soft 18 vs 9, Ten, the reason why hitting is optimal is the likelihood of getting small cards like 2 or 3 while getting the picture neither hurts or help. The ace slightly helps. But with the ace, hitting soft 18 in high count is more likely to catch the picture or the ace to soft 19, so it is likely hitting does not really hurt. The 6? It helps as more 6s cause the dealer to stand on 17 more often but the player does not like the 6 after a hit. Moreover, high count also suggests 6s are depleting too. If the dealer gets a BJ, both result in a loss anyway. Why the strategy becomes stand then?

    Many thanks
    The dealer already checked for BJ and does not have it, "no ten value cards under" there is a good chance that he may end up busting with a TC of +1 or above or having a 6 or 7 under. Against a dealer 9 or 10 up card there very well may be a ten underneath so you hit.
    Last edited by BoSox; 05-26-2020 at 05:27 PM.

  3. #3


    1 out of 1 members found this post helpful. Did you find this post helpful? Yes | No
    Quote Originally Posted by PromVRT View Post
    I see from Stanford Wong at in S17 game for A7 (soft 18) vs A, at TC above +1 the strategy becomes stand instead of hit. I checked with Wizard in the calculator by reducing the number of low cards outstanding, the strategy really changes from hit to stand.

    Basically, I do not understand the logic. Soft 18 vs 9, Ten, the reason why hitting is optimal is the likelihood of getting small cards like 2 or 3 while getting the picture neither hurts or help. The ace slightly helps. But with the ace, hitting soft 18 in high count is more likely to catch the picture or the ace to soft 19, so it is likely hitting does not really hurt. The 6? It helps as more 6s cause the dealer to stand on 17 more often but on the other hand the player does not like the 6 after a hit as well to hard 14. Moreover, high count also suggests 6s are depleting too. If the dealer gets a BJ, both result in a loss anyway. Why the strategy becomes stand then?

    Many thanks
    This is not what we call a very "volatile" play. At +1, standing is barely better than hitting -- by about 0.5%. All the way at +10, standing is still just 4% better than hitting. But the short answer is: we stand because the math says it's better to do so. Sometimes, the intuition behind plays is easy to see; sometimes, not so much.

    Don

  4. #4


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    Wizard also shows this:

    "Two decks, dealer stands on soft 17: Stand soft 18 vs A with 3 or more cards."

    "Four or six decks, dealer stands on soft 17: Stand soft 18 vs A with 4 or more cards."

    https://wizardofodds.com/games/black...stand-soft-17/

    Note that these are just basic strategy multi-card decisions. Also, that link says "one deck, dealers stands on soft 17. Scroll down to see these exceptions I posted for multiple decks.

  5. #5


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    Quote Originally Posted by DSchles View Post
    This is not what we call a very "volatile" play. At +1, standing is barely better than hitting -- by about 0.5%. All the way at +10, standing is still just 4% better than hitting. But the short answer is: we stand because the math says it's better to do so. Sometimes, the intuition behind plays is easy to see; sometimes, not so much.

    Don
    I trust the figure, if the situation happens to me I would stand as well. I just want to know any rationale behind the play. For example,

    Hit 12 vs 3: The gain by getting a pat hand is higher than the loss by busting with a picture card.
    Split 9 vs 9: The gain by pushing the 19 or winning double when the dealer gets unlucky and busts is greater than the risk of losing double.
    Hit A7 vs 9 and T: Many hands of 18 are losing to 19 or 20 anyway, so it does not matter whether you are at 17, 18 or bust when the dealer can beat. The gain by having stronger hand to beat or push the dealer is higher than the loss by unnecessarily busting or dealer has pat 17.

    Hit A7 vs A: This play (hit) surprises me as well in the beginning as regardless of the game (US or ENHC), it is not possible to beat dealer BJ with soft 18 as a starting hand. At first, it makes sense more to stand anyway because improving to 20 or 21 cannot beat BJ (for example, in ENHC where you do not know earlier if the dealer has BJ or not). However, BS says hit but shifts to stand at over TC>+1. I try to figure out anyway for possible explanation to the maths. Regardless, as long as I can memorize I would stand anyway.

  6. #6


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    Quote Originally Posted by PromVRT View Post
    I trust the figure, if the situation happens to me I would stand as well. I just want to know any rationale behind the play. For example,

    Hit 12 vs 3: The gain by getting a pat hand is higher than the loss by busting with a picture card.
    Split 9 vs 9: The gain by pushing the 19 or winning double when the dealer gets unlucky and busts is greater than the risk of losing double.
    Hit A7 vs 9 and T: Many hands of 18 are losing to 19 or 20 anyway, so it does not matter whether you are at 17, 18 or bust when the dealer can beat. The gain by having stronger hand to beat or push the dealer is higher than the loss by unnecessarily busting or dealer has pat 17.

    Hit A7 vs A: This play (hit) surprises me as well in the beginning as regardless of the game (US or ENHC), it is not possible to beat dealer BJ with soft 18 as a starting hand. At first, it makes sense more to stand anyway because improving to 20 or 21 cannot beat BJ (for example, in ENHC where you do not know earlier if the dealer has BJ or not). However, BS says hit but shifts to stand at over TC>+1. I try to figure out anyway for possible explanation to the maths. Regardless, as long as I can memorize I would stand anyway.
    Back to basics, huh.

  7. #7


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    A7 VS ACE @ tc +1 is stand also in games with European No Hole Card ?

  8. #8


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    Yes
    G Man

  9. #9


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    thanks

  10. #10


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    Quote Originally Posted by PromVRT View Post
    I trust the figure, if the situation happens to me I would stand as well. I just want to know any rationale behind the play
    You got part way there in your original post when you said that catching a 2 or 3 helps a lot, catching an A helps a bit and catching a T makes no difference. So what changes when the count goes up? Fewer 2s and 3s (these now help less), a few more aces (helps a bit more) and substantially more Ts (no effect).

    The net effect is that the value of hitting drops while the value of standing increases although, as Don says, neither does so substantially. At TC=0, the difference between hitting and standing is tiny, so even a small change in the relationship is enough to change the decision.

  11. #11


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    Quote Originally Posted by PromVRT View Post
    I see from Stanford Wong at in S17 game for A7 (soft 18) vs A, at TC above +1 the strategy becomes stand instead of hit. I checked with Wizard in the calculator by reducing the number of low cards outstanding, the strategy really changes from hit to stand.

    Basically, I do not understand the logic.
    Here is the answer to your questions.

    See the attached PDF.

    For standing A7 v A
    CC = Correlation Coefficient, AACpTCp = Average Advantage Change per True count point, Idx = infinite deck Index
    Count.................. CC........AACpTCp......Idx
    HL.......................50%.........0.5%........1 .4
    3m6c...................70%.........1.7%........0.5
    HL + 3*(3m6c)......85%.........0.5%.......1.3

    So HL + 3*(3m6c) is a very powerful count for standing on A7 v A.
    Note AACpTCp of HL + 3*(3m6c) is the same as the AACpTCp of HL at 0.5% But that ignores the fact that HL + 3*(3m6c) has a much higher SD than HL and so HL + 3*(3m6c) hits an index of 1.3 much more often than that HL hits an index of 1.4.

    The logic behind standing on psrc = HL + 3*(3m6c) >= 1.3*dr where dr = decks remaining and psrc = playing strategy running count is that as 3m6c increased there is a deficiency of 3's and an excess of 6's left in the shoe. That means a large 3m6c means is is less likely that if player hit his A7 he would pick up a 3 for a perfect 21 and more likely that he would pick up a 6 for a stiff. Also with excess 6's it is more likely that the dealer has a six in the hole giving dealer an A6 which dealer must stand on in the S17 game and you automatically win by standing on your A7 v A.

    With EoR and LSL technique, answers to all blackjack strategy variations can be answered correctly and quickly.

    So here is the attached PDF with the LSL calculations and index, CC and AACpTCp calculations.
    A7 v 7 stand.pdf
    Last edited by bjanalyst; 08-29-2020 at 12:22 AM.

  12. #12


    3 out of 3 members found this post helpful. Did you find this post helpful? Yes | No
    Since it is 100% certain that the OP has no clue about anything you're talking about and probably uses Hi-Lo, where 3 and 6 both have identical tag values of +1, why don't you try to stop advertising your count and try to explain the +1 index for Hi-Lo.

    Don

  13. #13


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    Don - He's just like T3, for whom my catchphrase was, "if you can't dazzle them with brilliance, baffle them with bullshit."

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