Is Covering an OP's DD with my own DD @ final hand a loser's bet ?

Discussion in 'Blackjack Tournament Strategy' started by KungFox, Sep 16, 2019.

  1. KungFox

    KungFox Member

    Hello all,
    I hope you had a nice summer, as tourneys-filled as mine !

    One 'quandary' I often come across at the final hand of a table, be it final or elimination, is to bet (or not to bet) so as to cover an opponent's double down with my own double down .

    My feeling is that preparing to cover a DD with my own DD only applies against aggressive, not-so-savvy players, as an expert would rather play optimal most of the time. Or am I being delusional ?

    How often, or in which kinds of situations, do you cover OP's DD with your own DD ?

    I guess this discussion must already have taken place here in the past, but I couldn't find a relevant topic title during my searches...

    Thank you in advance for your lights !

    Greetings from Belgium,
  2. gronbog

    gronbog Top Member

    It sounds like you are asking about sizing your bet so as to be able to cover an opponent's possible double/split with a double/split of your own. If so, I would recommend always doing so as long as betting the extra amount does not cost you something more valuable.

    For example, you will lose about 48% to 49% of your hands. An opponent who intends to double/split anything will succeed about 32% of the time. So if betting the amount needed to possibly cover the double/split means you must bet more than your lead plus a chip, and you think that if you make that bet then your opponent will bet small enough to beat you if you lose (this is called taking the low), then you have covered an outcome which occurs 32% of the time at the cost of exposing yourself to an event which occurs 48% of the time. This is a bad trade off.

    I use this method of trading off possible outcomes to size all of my critical bets.
  3. KungFox

    KungFox Member

    Exactly. Sorry if I don't fully master the TBJ player's jargon yet.

    So, if I understood you right, covering a double/split is "a priori" not a bad move, especially if I am quite sure about the profile of my opponent(s) ? Do the "doubling anything" odds add, when against two opponents ? If so, covering their DD would be more "productive" (64 % vs. 48-49 %), or wouldn't it ?

    OK. But doesn't this then open the door for a possible, so-called "surrender trap" I would then have sprung "by the way", making this "coverbet" not so bad after all ?

    Thank you for your time !
    Last edited: Sep 18, 2019
  4. BughouseMaster

    BughouseMaster Active Member

    Surprised gronbog never replied back to you.
  5. KungFox

    KungFox Member

    Questions still stand, so anyone is welcome to jump in !

    Thanks for "exhuming" this thread anyway !
  6. gronbog

    gronbog Top Member

    Somehow I missed that post. Thanks for pointing it out.
    Right. The probability that your opponent(s) will make this move in the first needs to be considered. A basic strategy player will double/split a lot less often than a seasoned tournament player.

    When considering two or more opponents, you can not just add the probabilities. You need the probability that one or more of them will succeed. This is best calculated by obtaining the probability that none of them will succeed and then subtracting that from 1. Assuming that their chances for success are independent (and I don't know for sure that this is true), and knowing that each independently succeeds 32% of the time and fails 68% of the time, then the probability of 2 opponents both failing would be 0.68 * 0.68 = 0.4642 (46.42%). The probability of one or both of them succeeding is then 1 - 0.4642 = 0.5376 (53.76%)

    Yes, the possibility of surrendering to retake the low or the high definitely makes the play stronger than if surrender is not available.
  7. KungFox

    KungFox Member

    Again, thank you for these precious insights and corrections, posted just before a couple of major tournaments I'm going to attend in Germany and Austria !

    Looks like you slowly became, year after year, the main "Mister Q&A" of this forum ! ^^
  8. London Colin

    London Colin Top Member

    The 'surrender trap' plays very little part in it, though. That's just the extreme (and rare) case, where surrendering yields a lock.

    More generally you are faced with a choice of surrender/double/hit-to-some-total, and the tricky task of evaluating, based on the cards dealt to both players (as well as your assessment of how your opponent is likely to play their dealt cards), which of these actions gives you the highest chance of success.
    KenSmith likes this.
  9. KungFox

    KungFox Member

    Is there any specific best "order", "roadmap" to follow when at the final hand ? Do you first check the probability of being paid by your OPs according to their hands, or do you rather reason in terms of bankrolls/scores/chips ? Or am I getting misleaded ?

    Sorry for all this asking, but why reinvent the wheel when you know cars are rolling on the other side of the Ocean / Channel ? :)
  10. KenSmith

    KenSmith Administrator Staff Member

    When sizing your bet, you should try to have a good idea where you will be if the dealer pays everyone (the “high”), and also where you will be if the dealer beats everyone (the “low”).

    Then when the cards are dealt you can begin to assess each player’s hand and likelihood of winning. At that point the playing strategies are your focus.

    A more complicated question is a roadmap for what to consider first while sizing your bet. I think there are already discussions along those lines here somewhere. But in general, the high and the low are the starting points.
    From there, you can begin to consider what happens if you or your opponents have a blackjack or double down.
  11. London Colin

    London Colin Top Member

    It's been a long time since I actually played in a tournament, and even longer since I was playing regularly (online). As a result, much of my knowledge of the subject seems to have evaporated.:(

    I can think of a couple of links from the past might be helpful to you, though. Both relate to the two-player scenario, rather than anything more complicated.

    Firstly, you mentioned the surrender trap. A very thorough, academic treatment of this was published by
    James Grosjean and Previn Mankodi. The original location now seems to be a dead link, but it can still be found with the aid of the 'Internet Wayback Machine' -

    Secondly, there is a very old thread in which I replied to someone asking a similar question to the one you raised at the start of this one. (I get some praise from Ken in it, but I swear that's not why I am resurrecting it.:)) -
  12. KungFox

    KungFox Member

    Very interesting attic findings, Colin, thank you ! And also thank you Ken for this standard "feuille de route" once at the final hand.

    I guess I should have digged much deeper than till 2015 into the archives of this forum before asking : many nuggets seem to lay hidden beneath... ^^

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