MLS--fun with the team statistics and the poisson distribution

Discussion in 'Statistics and Analysis' started by JG, Nov 2, 2003.

  1. JG

    JG Member+

    Jun 27, 1999
    On the thread that inspired the formation of this forum, we discussed ways to predict team records from their goals scored and goals against. It was determined that using a Poisson distribution for goals would work well.

    I did some playing with this year's MLS's what I found.

    First I compared each teams actual points to their predicted points:

    [size=2]Team         GF  GA  Pts PrPts  Diff
    Chicago      53  43  53  47.91  +5.09 
    MetroStars   40  40  42  41.10  +0.90
    New England  55  47  45  46.60  -1.60  
    DC United    38  36  39  42.36  -3.36
    Columbus     44  44  38  41.31  -3.31
    San Jose     45  35  51  48.08  +2.92
    Colorado     40  45  40  37.87  +2.13
    Kansas City  48  44  42  44.02  -2.02
    Los Angeles  35  35  36  40.78  -4.78
    Dallas       35  64  23  24.22  -1.22
    "PrPts" is predicted points.

    The average error of 2.7 points is comparable to what I've gotten with European leagues.

    Next, I compared each teams predicted record to their predicted record if they had scored/allowed a league average amount of goals (43.3), generating a number for how many points their offense and defense had earned of lost...for example, Chicago
    won just over two games by scoring 53 goals instead of 43.3.

    [size=2]Team          Off    Def 
    Chicago      +6.45  +0.20  
    MetroStars   -2.34  +2.16  
    New England  +7.67  -2.36   
    DC United    -3.83  +4.87  
    Columbus     +0.49  -0.45  
    San Jose     +1.18  +5.64  
    Colorado     -2.31  -1.07  
    Kansas City  +3.20  -0.45  
    Los Angeles  -6.11  +5.50  
    Dallas       -5.25  -11.07  
    By comparing the amount of goals scored above/below the league average with the offensive rating in the above table, we can get the amount of "goals per win" for each team--for example Chicago scored 9.7 goals above the league average, which helped their team earn 6.45 points. 9.7/6.45*3=4.51 goals per win.

    [size=2]Team         Off    Gls   GPW
    New England +7.67  +11.7  4.58
    Chicago     +6.45  +9.70  4.51
    Kansas City +3.20  +4.70  4.41
    San Jose    +1.18  +1.70  4.32	
    Columbus    +0.49  +0.70  4.29
    Colorado    -2.31  -3.30  4.29  
    MetroStars  -2.34  -3.30  4.23
    DC United   -3.83  -5.30  4.15
    Dallas      -5.25  -8.30  4.74
    Los Angeles -6.11  -8.30  4.08
    "Gls" = goals scored vs. the league average.
    GPW = goals per win.

    So an MLS team needs to score 4-5 extra goals over a season to win another game...with the exception of Dallas the higher-scoring teams need to score a bit more to win another game. For defenses the numbers are a bit higher, but still between 4 and 5 goals needed to make a one-game difference.
  2. JG

    JG Member+

    Jun 27, 1999
    Formatting tables is fun.
  3. superdave

    superdave Member+

    Jul 14, 1999
    VB, VA
    DC United
    Nat'l Team:
    United States
    Please clarify something. Bill James found in the 80's (with the offensive explosion since then, the numbers probably don't still hold) that a team needed to get 10 extra runs to move up a full game over .500. By that I mean, if you outscore your opponents by 20, you expect to go 83-79, NOT 82-80. When you talk about winning an extra game, do you also mean NOT LOSING an extra game? If you outscore your opposition by 9, will you win 2 more games than you lose, or 4?

    It's probably obvious from your chart, but I don't have the statistical background for that. Anyway, if in my example it's 4 games, that sounds about right to me, but I'm still a bit surprised the number isn't lower. If it's 2 games, then I'm really surprised.
  4. beineke

    beineke New Member

    Sep 13, 2000
    Great work ... IMO, this is a very interesting result. Intuitively, I would've thought that fewer goals would buy you an extra win.

    At some point, I'd like to go back to those save percentages and see how much of a difference a good shot-stopper might make.
  5. JG

    JG Member+

    Jun 27, 1999
    Re: Re: MLS--fun with the team statistics and the poisson distribution

    Yeah, that's what I mean...a team that outscores its opponents by 9 goals would be about 4 games over .500.

    The number of goals to get the extra win increases as teams get farther from .500...but usually that's not a huge problem in MLS.
  6. ChrisE

    ChrisE Member

    Jul 1, 2002
    Nat'l Team:
    American Samoa
    Re: Re: MLS--fun with the team statistics and the poisson distribution

    Beineke, I compiled, I believe, teams' save percentages throughout MLS history. I tried doing a regression analysis, but seeing as it was the first time I'd ever tried anything remotely like that, I botched it pretty badly. If you feel like doing the work, I can give you the numbers.

    (sorry to hijack your thread, JG)
  7. beineke

    beineke New Member

    Sep 13, 2000
    From what I remember, after we adjusted for offsides, there was maybe a 10% gap from the best shotstopping defense to the worst (although most teams were nearly indistinguishable). If a team allows 5 shots on goal per game, the goalkeeping gap would be 15 goals over an entire season ... and 15 goals maps out to about 10 extra points.

    Conclusion: Because the Burn finished 13 points behind LA, even Tim Howard couldn't have gotten them into the playoffs.

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