THE BOOK--Playing The Percentages In Baseball

Thursday, September 30, 2010

How much of an advantage is HFA in the post-season?

Obviously that is an easy one to figure, unless there are “funny things” going on.

The reason why I brought it up was because of this dumb (at least the playoff part) blog entry in ESPN insider:

http://insider.espn.go.com/mlb/blog?name=olney_buster&id=5632321

It is by Buster Olney and it is titled “Why playing at home in the playoffs is no help” on the main ESPN baseball page and then, “The home-field advantage myth” on the blog page.

“On Sept. 22, the Yankees and Twins were tied for the best record in baseball at 92-60. The Rays were just 1.5 games back at 90-61. The Twins had already clinched the AL Central and the Yankees and Rays had firm grips on the AL East and wild-card spots.

“The three teams still had home-field advantage to play for, but it seems like no one really wanted it. Since Sept. 23, the Twins have gone 1-5, the Yankees have gone 2-5 and the Rays have gone 4-3. Hardly spectacular play from three of the best teams in baseball—but maybe they are on to something. Since 1995 (in the wild card era), the team with home-field advantage in the division series has won just 31 of the 60 series. Since the division series adopted a 2-2-1 format in 1998, the team with home-field advantage has won 25 of 48 series. (It was a 2-3 format from 1995 to 1997).

“It’s a similar story when we get to the league championship series. Teams with home-field advantage in the LCS are actually under .500 since it began in 1969: 39-41. The win percentages for division series since ‘95 for the team with the ‘advantage’ are just .517, while in the championship series, the ‘advantaged team’ has a .488 win percentage.”

So the team with HFA in the division series “only” won 31 of 60 series?  That is 52%.  Guess how often they are supposed to win (whether it is a 2-3 format or 2-2-1 makes no difference of course), assuming both teams are equal?  52%!

In the LCS, which is best of 7 of course, the record of the team with the HFA is 39-41,which is .488.  They are supposed to win 51% of the time, again, assuming equal teams.  One SD in 80 games is 5.6%, so .488 is a cool 1/5 of a standard deviation, essentially no information at all (other than the null hypothesis - or close to it - is likely to be true).

Of course looking the results of these numbers and not knowing the relative strengths of the two teams is worthless information to begin with.

Couldn’t the author (Olney) bother to ask someone with a little math smarts what the theoretical advantage for the team with HFA is in a 5 or 7 game series?

Sports journalism really contributes to the dumbing down of America, in my opinion, but we talk about that, or at least imply it, nearly every day on this blog, don’t we?

Speaking of, that would be a good title/subject for a college course (seriously) - “Sports Journalism and the Dumbing Down of America!”