See the top rated post in this thread. Click here

Page 3 of 6 FirstFirst 12345 ... LastLast
Results 27 to 39 of 70

Thread: Session Bankroll Question

  1. #27


    Did you find this post helpful? Yes | No
    Don - what goes on with the BJA books? First Zee's book disappears in a hotel and now this one...

  2. #28


    1 out of 1 members found this post helpful. Did you find this post helpful? Yes | No
    Quote Originally Posted by DSchles View Post
    I'm assuming you don't have BJA3 and are not familiar with the "premature bumping into the barrier syndrome" that I describe beginning on page 122. It's a very important idea, and it's precisely applicable to your question.

    In any event, I recalculated the s.d. based on your description of the betting style and frequencies of the various bet sizes. Instead of 1.14, I get about 1.76, so you can see how that's rather important. We now have that e.v. for 320 hands is -$160, while s.d. is more along the lines of $2,361 (which is: 1.76 x $75 x 320^0.5). So, you can see that a one-s.d. loss AT THE END of the four hours is -$2,521, and that occurs roughly 16% of the time. But, what you don't know is that the probability of losing that amount is roughly DOUBLE the 16%, because of the barrier phenomenon that I mentioned above.
    I found the calculator on https://www.qfit.com/blackjack-calculator-c3.htm, and the numbers match what you have said. I'm wondering how you arrive at 1.76 for stdev? My gut tells me it is still 1.14.

  3. #29


    Did you find this post helpful? Yes | No
    Quote Originally Posted by 21forme View Post
    Don - what goes on with the BJA books? First Zee's book disappears in a hotel and now this one...
    i guess it grew a pair of legs and walked away. I remember this one being my favorite book tho out of all other authors.

  4. #30


    Did you find this post helpful? Yes | No
    Quote Originally Posted by FishBear View Post
    I found the calculator on https://www.qfit.com/blackjack-calculator-c3.htm, and the numbers match what you have said. I'm wondering how you arrive at 1.76 for stdev? My gut tells me it is still 1.14.
    I also dont see how the STD would go from 1.14 all the way to 1.76 just bec of a fluctuating bet size from 50-75-100-125??? Bec first of all the initial bet is $50 not $75.... and he is only increasing on a WIN but standing pat at 50 on a loss (positive prog).

  5. #31


    Did you find this post helpful? Yes | No
    Quote Originally Posted by 21forme View Post
    Don - what goes on with the BJA books? First Zee's book disappears in a hotel and now this one...
    Clearly, it isn't worth holding on to!

    Don

  6. #32


    Did you find this post helpful? Yes | No
    Quote Originally Posted by FishBear View Post
    I found the calculator on https://www.qfit.com/blackjack-calculator-c3.htm, and the numbers match what you have said.
    Thanks for the vote of confidence. I feel much better that I apparently did it properly.

    Quote Originally Posted by FishBear View Post
    I'm wondering how you arrive at 1.76 for stdev? My gut tells me it is still 1.14.
    See BJA3, p. 20. Your gut is wrong.

    Don

  7. #33


    Did you find this post helpful? Yes | No
    Quote Originally Posted by BughouseMASTER View Post
    I also dont see how the STD would go from 1.14 all the way to 1.76 just bec of a fluctuating bet size from 50-75-100-125??? Bec first of all the initial bet is $50 not $75.... and he is only increasing on a WIN but standing pat at 50 on a loss (positive prog).
    If you're asking a question, and you don't have BJA3, then perhaps I can explain to you how to square the bet sizes, multiply each line by the variance, then the frequencies, sum vertically, and then take the square root of the sum, to get the overall s.d.

    If you're trying to tell me that you're so startled by the calculation that it must be wrong, well, then, I can't really help you.

    Don

  8. #34


    Did you find this post helpful? Yes | No
    I dont own BJA3. Sure you can tell me how to calculate that'd be great.

    TO avoid clutter here, I was actually trying to PM you but dont see a way to do that.... anyone if there's a way to PM someone on this server?

  9. #35


    Did you find this post helpful? Yes | No
    Quote Originally Posted by BughouseMASTER View Post
    I don't own BJA3. Sure you can tell me how to calculate that'd be great.

    TO avoid clutter here, I was actually trying to PM you but don't see a way to do that.... anyone if there's a way to PM someone on this server?
    You went to the right place, but you asked to be a friend, which, normally, I don't accept. You needed to simply send a message (email) by putting in DSchles in the "To" box.

    In any event, maybe an example will help you to understand some fundamental concepts.

    Suppose you flat bet $5 a hand for 100 hands. What is the overall s.d. for that? Well, the one-hand s.d. is 1.15 x $5, which is $5.75. Since overall s.d. is a square root function, the total s.d. for 100 hands is $5.75 x 100^0.5 = $5.75 x 10 = $57.50. Simple and straightforward, right?

    So, now, let's consider someone who bets $1 a hand for 50 hands and $9 a hand for another 50 hands. Clearly, that person has an average bet of the same $5 as above, and so you might be tempted to use that value and conclude that the overall s.d. for the 100 hands is the identical $57.50 as above, but you would be very wrong to do so!

    As I mentioned in my previous post, if bet sizes are different (makes no difference if you are spreading as a card counter, playing progression, or whatever), you cannot use the average bet size to calculate s.d. Instead, you need to use a somewhat more complicated process that involves: using the variance (the square of s.d.), multiplying by the square of the bet size, multiplying by the frequency of that particular bet, summing all the horizontal lines vertically, and, finally, taking the square root of that sum.

    Wow! All that, huh? Yup. and there are no shortcuts; that's the way to do it. Period. So, instead of getting the $57.50 that you thought might be the s.d. for the second example, what is the correct answer? Well, let's follow my instructions above:

    Variance is 1.3225. First bet squared is 1. Second bet squared is 81. Frequency of each bet is 50 (hands). So, ...

    [(1.3225 x 1 x 50) + (1.3225 x 81 x 50)]^0.5 = (66.125 + 5,356.125)^0.5 = 5,422.255^0.5 = 73.64. Oh!! So, $73.64 instead of $57.50, despite the same average bet of $5 each time.

    Clear?

    Don

  10. #36


    1 out of 1 members found this post helpful. Did you find this post helpful? Yes | No
    Quote Originally Posted by DSchles View Post
    You don't seem to understand that it has just become annoying.

    Don
    +1
    Please, Wave, loose (sic) the pictures, or at least get some new material.

  11. #37


    Did you find this post helpful? Yes | No
    Quote Originally Posted by DSchles View Post
    You went to the right place, but you asked to be a friend, which, normally, I don't accept. You needed to simply send a message (email) by putting in DSchles in the "To" box.

    In any event, maybe an example will help you to understand some fundamental concepts.

    Suppose you flat bet $5 a hand for 100 hands. What is the overall s.d. for that? Well, the one-hand s.d. is 1.15 x $5, which is $5.75. Since overall s.d. is a square root function, the total s.d. for 100 hands is $5.75 x 100^0.5 = $5.75 x 10 = $57.50. Simple and straightforward, right?

    So, now, let's consider someone who bets $1 a hand for 50 hands and $9 a hand for another 50 hands. Clearly, that person has an average bet of the same $5 as above, and so you might be tempted to use that value and conclude that the overall s.d. for the 100 hands is the identical $57.50 as above, but you would be very wrong to do so!

    As I mentioned in my previous post, if bet sizes are different (makes no difference if you are spreading as a card counter, playing progression, or whatever), you cannot use the average bet size to calculate s.d. Instead, you need to use a somewhat more complicated process that involves: using the variance (the square of s.d.), multiplying by the square of the bet size, multiplying by the frequency of that particular bet, summing all the horizontal lines vertically, and, finally, taking the square root of that sum.

    Wow! All that, huh? Yup. and there are no shortcuts; that's the way to do it. Period. So, instead of getting the $57.50 that you thought might be the s.d. for the second example, what is the correct answer? Well, let's follow my instructions above:

    Variance is 1.3225. First bet squared is 1. Second bet squared is 81. Frequency of each bet is 50 (hands). So, ...

    [(1.3225 x 1 x 50) + (1.3225 x 81 x 50)]^0.5 = (66.125 + 5,356.125)^0.5 = 5,422.255^0.5 = 73.64. Oh!! So, $73.64 instead of $57.50, despite the same average bet of $5 each time.

    Clear?

    Don
    Not exactly. So what would be the RoR on $9/hand for 50 hands and $1/hand for 50 hands? BTW - You gave me the 1st part of your email, but did not say the domain.

  12. #38


    Did you find this post helpful? Yes | No
    Quote Originally Posted by BughouseMASTER View Post
    Not exactly. So what would be the RoR on $9/hand for 50 hands and $1/hand for 50 hands? BTW
    How can I give you a ROR without a bankroll? In the calculator, just plug in the desired BR, the (negative) win rate per 100 hands, and the s.d. per 100 hands, which I've shown you how to calculate.

    Quote Originally Posted by BughouseMASTER View Post
    You gave me the 1st part of your email, but did not say the domain.
    It isn't an email address! It's the handle to put into the addressee field on the forum website.

    Don

  13. #39


    Did you find this post helpful? Yes | No
    I do not see how to msg/email you here still !!!

Page 3 of 6 FirstFirst 12345 ... LastLast

Similar Threads

  1. Optimal session bankroll
    By Bricklayer in forum General Blackjack Forum
    Replies: 14
    Last Post: 12-23-2019, 07:53 AM
  2. 'Session' bankroll ROR
    By Qh4Mate in forum General Blackjack Forum
    Replies: 59
    Last Post: 12-11-2019, 09:49 PM
  3. Minimum session bankroll..
    By ZeeBabar in forum General Blackjack Forum
    Replies: 11
    Last Post: 07-11-2017, 04:10 AM
  4. VerdugoJohn: Session Bankroll--LONG QUESTION
    By VerdugoJohn in forum Blackjack Beginners
    Replies: 11
    Last Post: 12-30-2005, 11:40 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

About Blackjack: The Forum

BJTF is an advantage player site based on the principles of comity. That is, civil and considerate behavior for the mutual benefit of all involved. The goal of advantage play is the legal extraction of funds from gaming establishments by gaining a mathematic advantage and developing the skills required to use that advantage. To maximize our success, it is important to understand that we are all on the same side. Personal conflicts simply get in the way of our goals.