Z Scores and all underdogs

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • genyes
    SBR Hustler
    • 01-14-06
    • 75

    #1
    Z Scores and all underdogs
    I am currently using a system to bet on soccer underdogs. I am betting very modest amounts at this time until I am very confident that the system is worthy of larger bets.
    My results so far are: 30 wins and 54 losses (betting the same amount each time) with a 12.7% ROI. The wagers range from slight underdogs up to 4-1 underdogs.


    I'm familiar with how to calculate Z-scores--except in this type of situation. How would you determine that the system is a good one i.e. worthy of your usual betting size?

    Thanks
    Last edited by genyes; 01-13-11, 08:30 AM.
  • the_mathman
    SBR Sharp
    • 01-04-11
    • 312

    #2
    Do you bet on 1X2 market or in the AH ?
    Comment
    • bztips
      SBR Sharp
      • 06-03-10
      • 283

      #3
      The variance formula for a single bet is:

      Variance = betsize^2 * (decimal odds-1)

      Compute this for all your bets, then add them up. Then take the square root of the sum to get the std. dev. for your z-score calculation.
      Comment
      • the_mathman
        SBR Sharp
        • 01-04-11
        • 312

        #4
        Z score is not enough.
        do you need to totalize a sample of at least 2000 bets distributed along the 12 month of the year.

        do you can try to use historical data (e.g.:http://www.betexplorer.com/) for test your method (if is possible)
        Comment
        • genyes
          SBR Hustler
          • 01-14-06
          • 75

          #5
          1X2
          Comment
          • Justin7
            SBR Hall of Famer
            • 07-31-06
            • 8577

            #6
            I don't agree with mathman.

            If you have a Z score of +2, that is very interesting. At +3, I would definitely bet it, especially if I understood and agreed with the logic behind it.
            Comment
            • Maverick22
              SBR Wise Guy
              • 04-10-10
              • 807

              #7
              @Justin7 So you calculate this Z-Score. What does that end up telling you? What does it buy you?
              Comment
              • bztips
                SBR Sharp
                • 06-03-10
                • 283

                #8
                Originally posted by Maverick22
                @Justin7 So you calculate this Z-Score. What does that end up telling you? What does it buy you?
                It tells you the probablility that the results you're getting are just by chance, given your current sample.
                Comment
                • the_mathman
                  SBR Sharp
                  • 01-04-11
                  • 312

                  #9
                  Originally posted by genyes
                  1X2

                  so, do you bet on underdog only or sometimes do you bet the X2 double chance (lay favorite)?
                  Comment
                  • the_mathman
                    SBR Sharp
                    • 01-04-11
                    • 312

                    #10
                    Originally posted by Justin7
                    I don't agree with mathman.

                    If you have a Z score of +2, that is very interesting. At +3, I would definitely bet it, especially if I understood and agreed with the logic behind it.
                    unfortunately, the betting world isnt so matematically 'clear' and for validate a selection system do you need a big sample with match distributed along all the year.....

                    (this is my opinion, of course, based on my esperience on the soccer betting)
                    Comment
                    • brettd
                      SBR High Roller
                      • 01-25-10
                      • 229

                      #11
                      Z scores are useful when you're betting on the line. 1x2 with the large variety of odds that one would take odds at would complexify Z score taking. I guess you would sort of have to place all of your bets in odds 'brackets' and wait to you got a sufficient sample in any given odds bracket. But even that would be rough (depending on how narrow you would bracket odds together).

                      I have the same problem as most of my betting is 1x2. I'm going to resort to Monte Carlo simulation to come to a solution.
                      Comment
                      • Data
                        SBR MVP
                        • 11-27-07
                        • 2236

                        #12
                        Originally posted by genyes
                        I am currently using a system to bet on soccer underdogs... How would you determine that the system is a good
                        I just use my crap detector program. It tells me immediately that the system you described in the first sentence is crap.
                        Comment
                        • greva
                          SBR Sharp
                          • 03-01-10
                          • 487

                          #13
                          Originally posted by Data
                          I just use my crap detector program. It tells me immediately that the system you described in the first sentence is crap.
                          How is this helpful?
                          Comment
                          • Peregrine Stoop
                            SBR Wise Guy
                            • 10-23-09
                            • 869

                            #14
                            I'd run a monte carlo and see where your results fall upon the distribution of possible outcomes
                            Comment
                            • Data
                              SBR MVP
                              • 11-27-07
                              • 2236

                              #15
                              Originally posted by greva
                              How is this helpful?
                              That was an attempt to point out that the prerequisite for using z-scores is formulating a rational theory for the source of +EV. "An underdog system" is one of the more frequently used names for yet another variant of coin flipping. There are zillions of these systems and some of them have the Z-scores that are as high as you want. Those systems are still 0EV. Using valid methods in inappropriate ways guarantees drawing false conclusion. Hope this helps.
                              Comment
                              • specialronnie29
                                SBR High Roller
                                • 09-19-10
                                • 140

                                #16
                                Originally posted by Justin7
                                I don't agree with mathman.

                                If you have a Z score of +2, that is very interesting. At +3, I would definitely bet it, especially if I understood and agreed with the logic behind it.
                                are you serious

                                didnt you write a book on gambling. how do you make any money when you believe this. if you look hard enough you can find a z-score of 20 by betting on teams with 5 vowels in their name on days when there is a full moon and your pet shit himself
                                Comment
                                • Justin7
                                  SBR Hall of Famer
                                  • 07-31-06
                                  • 8577

                                  #17
                                  Originally posted by specialronnie29
                                  are you serious

                                  didnt you write a book on gambling. how do you make any money when you believe this. if you look hard enough you can find a z-score of 20 by betting on teams with 5 vowels in their name on days when there is a full moon and your pet shit himself
                                  I think you missed the second requirement: I understand and agree with the logic. If there isn't a logical basis, the z-score is mostly useless.
                                  Comment
                                  • specialronnie29
                                    SBR High Roller
                                    • 09-19-10
                                    • 140

                                    #18
                                    no justin

                                    you wrote this: If you have a Z score of +2, that is very interesting. At +3, I would definitely bet it, especially if I understood and agreed with the logic behind it.

                                    you said you would bet anything at +3
                                    Comment
                                    • Justin7
                                      SBR Hall of Famer
                                      • 07-31-06
                                      • 8577

                                      #19
                                      Originally posted by specialronnie29
                                      no justin

                                      you wrote this: If you have a Z score of +2, that is very interesting. At +3, I would definitely bet it, especially if I understood and agreed with the logic behind it.

                                      you said you would bet anything at +3
                                      I stand corrected.

                                      For the record, I would not bet on any Z score unless I had a logic that explained the results.
                                      Comment
                                      • specialronnie29
                                        SBR High Roller
                                        • 09-19-10
                                        • 140

                                        #20
                                        the phrase z score should be banned from this subforum

                                        half the shit people are applying it to isnt even normally distributed
                                        Comment
                                        • bztips
                                          SBR Sharp
                                          • 06-03-10
                                          • 283

                                          #21
                                          Originally posted by specialronnie29
                                          the phrase z score should be banned from this subforum

                                          half the shit people are applying it to isnt even normally distributed
                                          Uh, Central Limit Theorem...
                                          Comment
                                          • the_mathman
                                            SBR Sharp
                                            • 01-04-11
                                            • 312

                                            #22
                                            do you remember always that sports aren't (totally) casual events!
                                            Comment
                                            • specialronnie29
                                              SBR High Roller
                                              • 09-19-10
                                              • 140

                                              #23
                                              Originally posted by bztips
                                              Uh, Central Limit Theorem...
                                              N = 74 from binomial distn

                                              can argue about whether that N is large but most guys come on here with a 10-2 record and want to know if it means theyve found the holy grail;
                                              Comment
                                              SBR Contests
                                              Collapse
                                              Top-Rated US Sportsbooks
                                              Collapse
                                              Working...