03 September, 2016

2016 Win Total Predictions (Through August 31)


These predictions are based on my own silly estimator, which I know can be improved with some effort on my part.  There's some work related to this estimator that I'm trying to get published academically, so I won't talk about the technical details yet (not that they're particularly mind-blowing anyway). These predictions include all games played before through August 31 break.

As a side note, I noticed that my projections are very similar to the Fangraphs projections on the same day. I'm sure we're both calculating the projections from completely different methods, but it's reassuring that others have arrived at basically the same conclusions. Theirs have also have playoff projections, though mine have intervals attached to them.

I set the nominal coverage at 95% (meaning the way I calculated it the intervals should get it right 95% of the time), but based on tests of earlier seasons at this point in the season the actual coverage is around 94%, with intervals usually being one game off if and when they are off.

Intervals are inclusive. All win totals assume a 162 game schedule.

\begin{array} {c c c c} 
\textrm{Team}  & \textrm{Lower}  & \textrm{Mean} & \textrm{Upper} & \textrm{True Win Total}  & \textrm{Current Wins/Games}\\ \hline
ARI & 63 & 68.82 & 74 & 71.61 & 56 / 133 \\
ATL & 57 & 62.25 & 68 & 68.41 & 50 / 133 \\
BAL & 81 & 86.57 & 92 & 81.42 & 72 / 133 \\
BOS & 85 & 90.41 & 96 & 91.7 & 74 / 133 \\
CHC & 98 & 103.63 & 109 & 100.59 & 85 / 132 \\
CHW & 71 & 76.85 & 83 & 77.61 & 62 / 131 \\
CIN & 62 & 67.9 & 74 & 69.67 & 55 / 132 \\
CLE & 87 & 92.68 & 98 & 90.03 & 76 / 132 \\
COL & 73 & 78.63 & 84 & 81.72 & 64 / 133 \\
DET & 81 & 86.95 & 92 & 83.51 & 72 / 133 \\
HOU & 81 & 86.24 & 92 & 85.14 & 71 / 133 \\
KCR & 78 & 83.09 & 89 & 78.69 & 69 / 133 \\
LAA & 67 & 72.93 & 78 & 77.8 & 59 / 133 \\
LAD & 84 & 89.44 & 95 & 86.26 & 74 / 133 \\
MIA & 76 & 81.66 & 87 & 81.91 & 67 / 133 \\
MIL & 65 & 70.13 & 76 & 73.34 & 57 / 133 \\
MIN & 56 & 61.98 & 68 & 70.1 & 49 / 132 \\
NYM & 78 & 83.61 & 89 & 81.58 & 69 / 133 \\
NYY & 78 & 83.86 & 90 & 80.28 & 69 / 132 \\
OAK & 64 & 69.88 & 75 & 71.92 & 57 / 133 \\
PHI & 67 & 72.42 & 78 & 69.38 & 60 / 133 \\
PIT & 77 & 82.37 & 88 & 80.33 & 67 / 131 \\
SDP & 63 & 68.73 & 74 & 74.14 & 55 / 132 \\
SEA & 77 & 82.55 & 88 & 81.3 & 68 / 133 \\
SFG & 82 & 88 & 94 & 86.39 & 72 / 132 \\
STL & 81 & 86.25 & 92 & 87.69 & 70 / 132 \\
TBR & 65 & 70.72 & 76 & 79.47 & 56 / 132 \\
TEX & 89 & 94.45 & 100 & 83.61 & 80 / 134 \\
TOR & 86 & 91.93 & 97 & 89 & 76 / 133 \\
WSN & 89 & 94.82 & 100 & 94.01 & 78 / 133 \\
 \hline\end{array}

These quantiles are based off of a distribution - I've uploaded a picture of each team's distribution to imgur. The bars in red are the win total values covered by the 95% interval. The blue line represents my estimate of the team's "True Win Total" based on its performance - so if the blue line is to the left of the peak, the team is predicted to finish "lucky" - more wins than would be expected based on their talent level - and if the blue line is to the right of the peak, the team is predicted to finish "unlucky" - fewer wins that would be expected based on their talent level.

It's still difficult to predict final win totals even at the beginning of September - intervals have a width of approximately 11-12 games. The Texas Ranges have been lucky this season, with a projected win total over 10 games larger than their estimated true talent level!  Conversely, the Tampa Bay Rays have been unlucky, with a projected win total 10 games lower than their true talent level.

The Chicago Cubs have a good chance at winning 105+ games. My system believes they are a "true" 101 win team. Conversely, the system believes that the worst team is the Atlanta Braves, which are a "true" 68 win team (though the Minnesota Twins are projected to have the worst record at 62 wins).



Terminology




To explain the difference between "Mean" and "True Win Total"  - imagine flipping a fair coin 10 times. The number of heads you expect is 5 - this is what I have called "True Win Total," representing my best guess at the true ability of the team over 162 games. However, if you pause halfway through and note that in the first 5 flips there were 4 heads, the predicted total number of heads becomes $4 + 0.5(5) = 6.5$ - this is what I have called "Mean", representing the expected number of wins based on true ability over the remaining schedule added to the current number of wins (from the beginning of the season until the all-star break).


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