2009 Baseball Predictions Primer

In the past (2008 and 2007) I have made predictions about the outcome of the baseball season. I based these on the previous year's record and then added in my own personal adjustment. It is a fairly simple formula.

Previous Years Wins +/- Off-season Moves.

This year I am taking a different approach. I have run some regression statistics and will be using those. I figured that I would explain the process before I actually posted the predictions. I have run a regression analysis on the premise that Win Total is a function of OPS and WHIP. To make it simpler, Winning is a combination of Hitting and Pitching. I chose OPS and WHIP as indicators of each respectively. Running a regression analysis on the past 5 seasons, I came up with this formula:

Win Total = 55.19 + (192.8 * OPS) - (86.2 * WHIP)

Now, you may ask, "How accurate is that formula?" A good question. According to the regression model, the adjusted R squared is .7835. In other words, The above formula accounts for 78.35% of the reason wins are the total that they are. For baseball, this is a fairly strong relationship. There is obviously no way to account for random occurrences fully, so a good 21.65% is still left to chance and situational factors.

So with that formula in mind. I calculated how many wins each team would have won if that formula were perfect. I then took the difference between reality and prediction and multiplied it by 78.35%. So with that, I have come up with the Adjusted Win Total for each team last year.

I will use this as my base prior to adjustment this year rather than actual results. Why do I want to do this? I want to know how good teams were, not how lucky they were. Therefore my formula this year is:

Previous Years Adjusted Wins +/- Opinion of Off-season Moves.

So what exactly are the adjusted win totals that I will be working with?

AL East

1. 96 - 66 Boston Red Sox


2. 92 - 70 Tampa Bay Rays


3. 89 - 73 Toronto Blue Jays


4. 87 - 75 New York Yankees


5. 68 - 94 Baltimore Orioles

AL Central

1. 91 - 71 Chicago White Sox


2. 84 - 78 Cleveland Indians


3. 84 - 78 Minnesota Twins


4. 76 - 86 Detroit Tigers


5. 75 - 87 Kansas City Royals

AL West

1. 88 - 74 Los Angeles Angels


2. 77 - 85 Texas Rangers


3. 72 - 88 Oakland Athletics


4. 61 - 101 Seattle Mariners

NL East

1. 88 - 74 Philadelphia Phillies


2. 85 - 77 New York Mets


3. 82 - 80 Florida Marlins


4. 77 - 85 Atlanta Braves


5. 63 - 99 Washington Nationals

NL Central

1. 98 - 64 Chicago Cubs


2. 87 - 75 Milwaukee Brewers


3. 87 - 75 St. Louis Cardinals


4. 81 - 81 Houston Astros


5. 71 - 91 Cincinnati Reds


6. 61 - 101 Pittsburgh Pirates

NL West

1. 86 - 76 Arizona Diamondbacks


2. 85 - 77 Los Angeles Dodgers


3. 74 - 88 Colorado Rockies


4. 70 - 92 San Diego Padres


5. 68 - 94 San Francisco Giants

Which team was adjusted the most?
Los Angeles Angels (-12 wins)

Feel free to post comments or suggestions. Is there a stat that you think would be better to use than either OPS or WHIP?