Postseason Odds, PECOTA version

Last update: Thu Jul 2 07:31:03 2009 PT



Playing the rest of the season a million times

with some help from PECOTA

by Clay Davenport

See the original version of this report, based entirely on real data (no projections). And the ELO version of this report, based on an ELO rating scheme.

Generated Thu Jul 2 07:17:39 EDT 2009


Average wins by position in AL East:  100.3 94.1 87.8 79.9 71.4
AL East           W    L    Pct3  Avg W  Avg L  Champions  Wild Card   Playoffs
Red Sox           48   30   .579   98.0   64.0   59.95202   30.01598   89.96799
Yankees           45   32   .582   95.0   67.0   33.77908   43.85153   77.63062
Rays              44   36   .534   88.3   73.7    5.85308   18.92091   24.77399
Blue Jays         42   38   .481   79.8   82.2     .40718    2.25837    2.66555
Orioles           35   43   .454   72.3   89.7     .00863     .09601     .10464

Average wins by position in AL Central:  88.7 83.3 78.5 72.2 66.4
AL Central        W    L    Pct3  Avg W  Avg L  Champions  Wild Card   Playoffs
Tigers            43   35   .485   86.0   76.0   53.60084     .60381   54.20464
Twins             41   39   .472   82.3   79.7   25.53681     .51386   26.05067
White Sox         40   38   .481   81.2   80.8   19.64100     .55076   20.19177
Royals            33   44   .436   70.5   91.5     .81188     .00937     .82125
Indians           31   49   .444   69.2   92.8     .40947     .00175     .41122

Average wins by position in AL west:  89.7 84.1 78.9 70.0
AL West           W    L    Pct3  Avg W  Avg L  Champions  Wild Card   Playoffs
Angels            42   34   .499   87.1   74.9   55.16251    1.14044   56.30294
Rangers           42   35   .470   82.6   79.4   23.12941     .91037   24.03978
Mariners          39   38   .492   82.5   79.5   21.04469    1.11576   22.16045
Athletics         33   44   .438   70.7   91.3     .66339     .01110     .67449

Average wins by AL Wild Card:  94.2

Average wins by position in NL East:  90.0 85.1 81.1 76.3 55.1
NL East           W    L    Pct3  Avg W  Avg L  Champions  Wild Card   Playoffs
Marlins           41   39   .479   81.2   80.8   13.93099    2.62399   16.55498
Phillies          39   36   .526   86.4   75.6   45.08389    4.64937   49.73326
Mets              38   39   .488   80.6   81.4   12.30244    2.49037   14.79281
Braves            37   40   .540   84.2   77.8   28.68268    4.76045   33.44312
Nationals         22   54   .380   55.1  106.9     .00000     .00000     .00000

Average wins by position in NL Central:  91.1 86.6 83.3 80.1 76.3 70.4
NL Central        W    L    Pct3  Avg W  Avg L  Champions  Wild Card   Playoffs
Brewers           42   36   .522   87.2   74.8   41.50625    7.34143   48.84768
Cardinals         42   38   .512   84.8   77.2   23.80241    6.67448   30.47690
Reds              38   38   .494   81.7   80.3   10.86209    4.41817   15.28025
Cubs              37   38   .519   83.8   78.2   19.35475    6.14076   25.49550
Astros            37   39   .476   78.3   83.7    4.11008    1.76338    5.87346
Pirates           36   42   .423   72.0   90.0     .36442     .15123     .51565

Average wins by position in NL West:  99.5 89.0 81.5 72.8 66.4
NL West           W    L    Pct3  Avg W  Avg L  Champions  Wild Card   Playoffs
Dodgers           50   29   .575   99.2   62.8   89.67892    7.70766   97.38658
Giants            42   35   .524   88.0   74.0    8.87037   39.42846   48.29883
Rockies           41   37   .467   82.3   79.7    1.43317   11.63349   13.06666
Padres            34   43   .423   70.7   91.3     .01246     .16344     .17589
Diamondbacks      31   47   .444   69.0   93.0     .00509     .05333     .05842

Average wins by NL Wild Card:  90.5

As the title says, the post-season odds report was compiled by running a Monte Carlo simulation of the rest of the season one million times. Current wins, losses and expected winning percentages are taken from the Adjusted Standings Report.

Expected winning percentages (EWP) for each team starts with their W3 and L3 from the Adjusted Standings. A regression is applied to derive the EWP for the rest of the season, which is going to be between the current winning percentage and .500. To allow for uncertainty in the EWP, a normal distribution centered on the EWP is randomly sampled, and that value is used for the remainder of the season in that iteration. To simulate the normal 4% home-field advantage, the home team gets a .020 point bonus, while the visitors take a 0.020 penalty. The likelihood of winning each game is determined by the log5 method.

At least, that's how it works in the regular version. For this, PECOTA adjusted version, the regression isn't done to the mean (.500), but rather to the PECOTA projection made at the beginning of the year (numbers which can be found here). The Yankees were projected to be a .580 team - and so the EWP described above will nudge their record towards .580, not .500. W and L are the team's wins and losses through yesterday's games.

Pct3 is the expected winning percentage, taken from W3 and L3, with the regression-to-mean component.

Avg W and Avg L are the average number of wins and losses each team finishes over the million season iterations.

Champions is how often, in percentage terms, this team won the championship of their division. Ties are not broken, but credited as 0.5 championships apiece (for a two-way tie), .333 apiece for a three-way tie, .25 for four-way, etc. This is why the final decimal place is not an error!

Wild Card is how often, in percentage terms, this team won the wild card. As with championships, ties are not broken, but apportioned among the tied teams.

Playoffs is how often, in percentage terms, the team either wins the division or the wild card.

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