Pythagorean Theoreom

[rluzinski]

One of the most simple useful statstical equations you can use in baseball is the "Pythagorean Theorem." Developed by Bill James, it is a way to coorelate runs scored and runs given up to a team's winning %. In it's simplest form:

 RS^2 Winning % = ------------- (RS^2 + RA^2) RS = Runs Scored RA = Runs Against 

 

The Pythagorean Theorem can be used to justify the "10 Run Rule" which says that adding 10 runs over the course of a season adds 1 win:

 

http://i14.photobucket.com/albums/a345/rluzinski/pythagorean.jpg

 

While obviously not an exact number (The difference between RS and RA affect the value of 10 runs), it's an excellant estimation.

 

Related Links:

 

Revisiting the Pythagorean Theorem

 

Google Search

 

More to Come!

[deeswan]

On this note, I've noticed that I can no longer access the "Expected Wins" stat at Baseball Prospectus. Is that now subscribers only?

[nsimps]

I thought they use an exponent of 1.82 now instead of 2.

[rluzinski]

I thought they use an exponent of 1.82 now instead of 2.

 

As the bp article I linked to explains, James later changed the 2 exponent to 1.82. That article outlines a couple other equations that can be used and I know of a few others myself. I just use the basic one since the difference for a team over the course of a year isn't very different anyway.