RedsManRick

03-12-2010, 10:19 AM

Tango has a good post up over on his blog discussion the ability of models to predict HR totals. Here's the part I found most illuminating regarding how variation and regression work in practice, but the whole article is worth a read if you are dubious about systematic predictions. (the short: they are as accurate as a systematic process can be, but still result in pretty big error bars on an individual basis)

Tango's Blog Post

(http://www.insidethebook.com/ee/index.php/site/comments/forecasting_home_runs_in_2009/)

(If you're not familiar with Tom Tango, aka Tangotiger, he's one of the leading sabermetricians, more heavily focused on the detailed quant stuff. He and some colleagues wrote a great book called, THE BOOK--Playing The Percentages In Baseball and done some work for various professional teams, including most recently the Mariners. The stuff on his blog isn't always the most accessible to the non math geeks among us, but it's usually pretty high quality stuff.)

Can we prove that? A simple forecasting system I developed is called Marcel The Monkey Forecasting System, or The Marcels, for short. It’s named after the monkey from the TV show Friends. I also like the name Marcel for the hockey great Marcel Dionne so even if the name looks dated, you can think of Dionne instead. Anyway, Marcel listed 13 players as having a forecasted mean of 28 or more home runs for the 2009 season. Here are those hitters:

40 Howard, Ryan

32 Rodriguez, Alex

32 Fielder, Prince

32 Dunn, Adam

32 Braun, Ryan

31 Pujols, Albert

31 Pena, Carlos

30 Thome, Jim

29 Dye, Jermaine

28 Delgado, Carlos

28 Cabrera, Miguel

28 Berkman, Lance

28 Beltran, Carlos

Now, remember what I said, and this is important: we are NOT forecasting Pujols to hit 31 HR in 2009. We forecasted him to hit 31 HR give or take 20 or 30 HR. You apply that same kind of thinking for each of the above players. And, we are NOT forecasting Ryan Howard to led the league with 40 HR. We ARE forecasting SOMEONE to hit around 50 HR. And these guys our among our best bets. With the top-end of each of these hitters close to 50 HR, obviously the average will be much lower.

How many HR did these players hit in 2009?

47 Pujols, Albert

46 Fielder, Prince

45 Howard, Ryan

39 Pena, Carlos

38 Dunn, Adam

34 Cabrera, Miguel

32 Braun, Ryan

30 Rodriguez, Alex

27 Dye, Jermaine

25 Berkman, Lance

23 Thome, Jim

10 Beltran, Carlos

4 Delgado, Carlos

As you can see, it runs the gamut from Delgado’s 4 to Pujols’ league-leading 47. These 13 hitters were forecasted to hit a combined 401 HR in 2009. And how many HR did they actually hit in 2009? 400. That’s right, Marcel nailed it.

So, the forecasting systems work… if you know how to properly interpret what it is they are trying to tell you.

Tango's Blog Post

(http://www.insidethebook.com/ee/index.php/site/comments/forecasting_home_runs_in_2009/)

(If you're not familiar with Tom Tango, aka Tangotiger, he's one of the leading sabermetricians, more heavily focused on the detailed quant stuff. He and some colleagues wrote a great book called, THE BOOK--Playing The Percentages In Baseball and done some work for various professional teams, including most recently the Mariners. The stuff on his blog isn't always the most accessible to the non math geeks among us, but it's usually pretty high quality stuff.)

Can we prove that? A simple forecasting system I developed is called Marcel The Monkey Forecasting System, or The Marcels, for short. It’s named after the monkey from the TV show Friends. I also like the name Marcel for the hockey great Marcel Dionne so even if the name looks dated, you can think of Dionne instead. Anyway, Marcel listed 13 players as having a forecasted mean of 28 or more home runs for the 2009 season. Here are those hitters:

40 Howard, Ryan

32 Rodriguez, Alex

32 Fielder, Prince

32 Dunn, Adam

32 Braun, Ryan

31 Pujols, Albert

31 Pena, Carlos

30 Thome, Jim

29 Dye, Jermaine

28 Delgado, Carlos

28 Cabrera, Miguel

28 Berkman, Lance

28 Beltran, Carlos

Now, remember what I said, and this is important: we are NOT forecasting Pujols to hit 31 HR in 2009. We forecasted him to hit 31 HR give or take 20 or 30 HR. You apply that same kind of thinking for each of the above players. And, we are NOT forecasting Ryan Howard to led the league with 40 HR. We ARE forecasting SOMEONE to hit around 50 HR. And these guys our among our best bets. With the top-end of each of these hitters close to 50 HR, obviously the average will be much lower.

How many HR did these players hit in 2009?

47 Pujols, Albert

46 Fielder, Prince

45 Howard, Ryan

39 Pena, Carlos

38 Dunn, Adam

34 Cabrera, Miguel

32 Braun, Ryan

30 Rodriguez, Alex

27 Dye, Jermaine

25 Berkman, Lance

23 Thome, Jim

10 Beltran, Carlos

4 Delgado, Carlos

As you can see, it runs the gamut from Delgado’s 4 to Pujols’ league-leading 47. These 13 hitters were forecasted to hit a combined 401 HR in 2009. And how many HR did they actually hit in 2009? 400. That’s right, Marcel nailed it.

So, the forecasting systems work… if you know how to properly interpret what it is they are trying to tell you.