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Thread: DI and N0 in Advanced AP Circumstance

  1. #1

    Default DI and N0 in Advanced AP Circumstance

    From Eliot Jacobson PhD- The Cause of Suffering is Desire ...

    I am going to take a time out to review the definition of DI and to introduce a new number, N_0. Here is Donald Schlesinger’s definition of DI from his book “Blackjack Attack, 3rd edition” (page 186). He defines DI,

    “…for the play all game, to be equal to one thousand times (for convenience of expression) the ratio of that game’s per-hand win rate to the per-hand standard deviation.”

    Let EV denote the expected value per hand. This is simply the edge the AP has over the house. Let SD denote the standard deviation for one hand. The value of SD gives a measure of the volatility of the game. Then, for a game where the AP is playing every hand, the value of DI is given by:

    DI = 1000x(EV/SD).

    The new statistic I’m going to be presenting in this post, N_0, is given by this equation:

    N_0 = (SD/EV)2

    The reader no doubt wonders what this number means and where it comes from. The glossary at bj21.com gives the following definition of N_0 for blackjack:

    “The number of hands (sometimes expressed in hours of playing time) theoretically required to be played with a certain set of rules and strategy (count, spread etc) before the player reaches his goal to be ahead by at least one standard deviation.”

    In other words, N_0 is the number of hands the AP has to play until the chances he is still losing after playing that many hands lies outside the first standard deviation. More simply, if the AP plays N_0 hands, then there is approximately an 84% chance he will be beating the house and only about a 16% chance that he will be behind. The number N_0 gives an idea of long the player will need to play to “get to the long run.” The smaller the value of N_0, the fewer hands it will theoretically take for the AP to beat the house.

    As the definition at bj21.com implies, for ordinary blackjack card counting, the values of N_0 are frequently measured in the tens of thousands of hands. At 100 hands per hour, the AP is looking at 100’s of hours of play to reach his N_0. Professional level blackjack card counting requires endless patience, travel and hard work to squeak out a small profit in the face of brutal variance. That’s why there are so few AP’s who are pure blackjack card counters.

    Last edited by zengrifter; August 26th, 2016 at 09:49 AM. Reason: typo
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  2. #2


    Hi Zen,

    Thanks for this information.

    Plus, have you got good sources and informations about CE ? Moreover do you know how "risk averse" is the CE in qfit software ?

    Maybe you can help me.

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