Saturday, July 5, 2008
What are your team's playoff odds? Check the standings
By Greg Agami Special to ESPN.com
The Tampa Bay Rays have the best record in baseball.
They own a three-game lead over the defending champion Boston Red Sox, and a nine-game lead over the New York Yankees. What are the chances the Rays will win the division crown, or at least earn a wild-card berth for their first-ever playoff appearance?
Now, by checking the ESPN baseball standings, you can learn that -- as of Saturday -- the previously hapless Rays have a 54.4 percent chance of winning the division, compared to 38.3 percent for the Red Sox and 3.6 percent for the Yankees. These percentages are calculated by coolstandings.com, which simulates the remainder of the regular season 1 million times -- every day -- to determine the playoff chances for every MLB team.
For every team, coolstandings determines the following odds:
DIV -- percent chance each team has of winning its division WC -- percent chance each team has of winning the wild card POFF -- percent chance each team has of making the playoffs
These playoff chances are shown in the last three columns of the ESPN.com standings page, and will be updated every day through the end of the regular season.
How are the percentages determined? The key is estimating how many runs each team will score, on average, against every opponent on its schedule. Coolstandings takes into account factors such as home vs. away team performance, remaining strength of schedule, run differential and league scoring averages. Previous season performance is also used, especially near the beginning of a new season.
Coolstandings even takes into account all of the MLB tiebreaker scenarios when determining divisional and wild-card chances.
Some factors aren't considered, including starting pitchers, trades, free-agent signings and injuries. Roster changes are indirectly taken into account because the model emphasizes recent team performance over older data.
The estimated runs for each team are plugged into a modified version of Bill James' Pythagorean Theorem to determine the odds of each team beating the other teams on its schedule. The data is regressed to the mean, so hot or cold starts don't weigh too heavily on the simulation. Random error is also added, since a .550 team may actually be an underachieving .600 team or an overachieving .500 team.
That's a lot of math, but does it work?
Luckily, baseball has been around for quite a while, so there's a lot of data for math geeks to drool over. The geeks at coolstandings have optimized their model against historical data going back to 1903, the first year the World Series was played. Since then, there have been 340 playoff teams, 1,766 non-playoff teams, and more than 160,000 games played.
By simulating every season since 1903 and comparing the projected results against the actual historical results, coolstandings has been able to evaluate and improve the accuracy of its model. For each range of playoff chances -- say between 40 and 49.9 percent -- the average playoff chances for those teams can be compared against the number of teams that actually made the playoffs. The average absolute error across all teams and dates is less than 2 percent, and is continually being improved.
So will the Rays bust through and clinch their first playoff spot? Their magic number is still rather high, but odds are in their favor at least for today. Check the ESPN.com standings page now and throughout the season to track your favorite team's playoff chances, and know where your team really stands.
Greg Agami is the CEO and co-founder of coolstandings.com.