Steven Engelhardt

Latest Cubs prediction: 110-54 (0.362 team OBP, 3.66 team ERA, underlying equation). (Previous predictions: 112-50, 113-49, 90-62)

We’ll have to see how Soriano’s broken finger affects the Cubs’ team OBP and thus the prediction.

Latest Cubs prediction: 112-50 (0.368 team OBP, 3.73 team ERA, underlying equation). (Previous predictions: 113-49, 90-62)

To contrast, a simple extrapolation of their current 28-19 record predicts 97-65. 97-65 seems a lot more realistic than 112-50.

The problems with my regression which “predicts” a baseball team’s win-loss record are the following:

1. The regression is extremely sensitive to the input parameters, many of which are quite unstable throughout the year. For example, one extra point (0.001) of team OBP results in 0.6 extra predicted wins.
2. The standard error of the prediction is quite high (4.68).
3. The regression doesn’t seem to be much better than linearly extrapolating a team’s current win-loss record to the entire season.

To demonstrate my point, a run of the regression against the current Cubs team statistics (0.371 team OBP, 3.81 team ERA) now predicts a record of 113-49, a swing of 23 wins in a matter of 15 days. This record would put them 3 wins shy of the regular season win record—first achieved by the 1906 Cubs (in a 152-game season) and again by Lou Piniella’s 2001 Seattle Mariners.

It’s clear that this new prediction is the consequence of the Cubs’ hot streak. Let’s hope they can keep it going.

I may be going out on a limb here so early in the season, but I just ran the Cubs’ current team OBP of 0.339 and ERA of 4.03 through the regression to come up with my prediction for this year’s win-loss record: 90-72.

Update 2008-04-08 11:13AM: Looks like I’m in good company. Baseball Prospectus is predicting 91-71.

On July 4, I predicted the Cubs would finish 86-76. A rerun of the regression with season-ending data also predicts 86-76.

Their actual record: 85-75.

Now that the important stuff is out of the way, congratulations on winning the NL Central! Go Cubs Go!

Update 2007-10-06 9:22PM: Damn.

Per request, I have calculated my predictions for the 2007 Chicago Cubs season.

Based on the Cubs’ current team OBP of .329 and team ERA of 3.94 (both from here), the regression predicts a final record of 86-76.

Since a naive extension of their current record of 41-40 predicts they will finish 82-80, it seems the Cubs have been playing better than their record indicates.

Cubs 2006 season record predictions:

May 9: 64-98
August 30: 66-96
Prediction using regression against final team statistics (.319 OBP, 4.74 ERA): 67-95
Actual record: 66-96

Not bad, if I do say so myself.

Since the regression is highly sensitive to team OBP it may not be particularly useful over long time frames. Fortunately for me the Cubs stank pretty consistently throughout the year.

Top of the 8th inning: Cubs tie the game at 7-7.

[12:43] <@ronin> what the hell are [the Cubs] doing, trying to win?
[12:44] <@SmooveB> ronin: no, they’re trying to keep it close
                   before they blow it in heartbreaking fashion,
                   probably because dusty ran out of pitchers

11th inning: Game tied at 7-7.

Top 11TH B:3 S:2 O:0
Angel Pagan singles on a ground ball to left fielder Jason Bay.

Top 11TH B:1 S:0 O:0
Jacque Jones singles on a ground ball to right fielder Rajai Davis. Angel Pagan to 3rd.

Top 11TH B:0 S:0 O:0
Michael Barrett singles on a line drive to left fielder Jason Bay. Angel Pagan scores. Jacque Jones to 3rd.

Top 11TH B:1 S:0 O:1
Matt Murton grounds out to first baseman Xavier Nady. Michael Barrett to 2nd.

Top 11TH B:2 S:2 O:2
Ronny Cedeno out on a sacrifice fly to center fielder Chris Duffy. Jacque Jones scores. Michael Barrett to 3rd.

Top 11TH B:4 S:0 O:2
Marty McLeary intentionally walks Derrek Lee.

Top 11TH B:1 S:2 O:2
With Ryan Dempster batting, Derrek Lee advances to 2nd on defensive indifference.

Top 11TH B:1 S:3 O:3
Ryan Dempster [the pitcher!] strikes out swinging.

————————— MIDDLE 11TH

Bottom 11TH B:1 S:2 O:0
Xavier Nady singles on a line drive to right fielder Jacque Jones.

Bottom 11TH B:0 S:0 O:1
Ryan Doumit grounds out, pitcher Ryan Dempster to first baseman Derrek Lee. Xavier Nady to 2nd.

Bottom 11TH B:1 S:2 O:1
Jose Castillo singles on a line drive to right fielder Jacque Jones. Xavier Nady scores.

Bottom 11TH B:0 S:0 O:1
Offensive Substitution: Pinch hitter Humberto Cota replaces Marty McLeary.

Bottom 11TH B:2 S:0 O:1
Humberto Cota singles on a ground ball to third baseman Aramis Ramirez. Jose Castillo to 2nd.

Bottom 11TH B:1 S:2 O:2
Chris Duffy flies out to left fielder Matt Murton.

Bottom 11TH B:4 S:0 O:2
Jose Bautista walks. Jose Castillo to 3rd. Humberto Cota to 2nd.

Bottom 11TH B:1 S:2 O:2
Freddy Sanchez singles on a line drive to right fielder Jacque Jones. Jose Castillo scores. Humberto Cota scores. Jose Bautista to 2nd.

Final: Cubs lose 10-9.

FYI, the Cubs currently have a 0.318 OBP and 4.77 ERA, and the regression analysis predicts 66 wins.

Based on a regression analysis of the 2005 season, the number of wins of a baseball team can be predicted by the equation W = -55.574 - 15.0869ERA + 609.516OBP. (F-stat = 64.19, R² = 0.826, SE_W = 4.68)

Unfortunately for Chicago Cubs fans, if they continue to maintain their current ERA of 4.57 and OBP of 0.310, I predict they will win 64 ± 9.36 games this year with a 95% confidence interval.