Question About "The Book"

[tweek]

I'm digging my way through "The Book," and came across an interesting equation they used, and can't figure out the rationale behind it for the life of me.

In Chapter 7 (Starting Pitchers), they do a lot of work comparing actual wOBA (which is their modified calculation of OBP) with "expected wOBA."

Their "expected wOBA" for any particular subset of matchups is calculated as follows:

wOBA_expected = wOBA_pitchers + wOBA_batters - wOBA_league_average

Can anyone help me understand where they would come up with this? I don't even have any clues at this point... so I'm open to any comments at all!

(Edit... should have been a (-) sign in front of wOBA_league_average)

[waiverwire]

Try asking the authors at their website: http://www.insidethebook.com/ee/

[tweek]

Yeah I sent a note. I also saw that I went to the same school as one of the authors. It's a really small school (<1000 people total), so hopefully he'll feel some comradery and respond!