Thursday, June 10, 2010

Fielding Independent Pitching (FIP) Isn't Fielding Independent

To understand how far from reality the names of some statistics are look no further than FIP.  This is an acronym for Fielding Independent Pitching.

According to Wikipedia the formula for this statistic is as follows:

FIP=\frac{13HR + 3BB - 2K}{IP}

You will notice IP  (innings pitched) is the denominator. The formula for a pitcher's IP is the number of outs made while he was pitching divided by 3.

Of course "outs" are hardly fielding independent. Even a pitcher who strikes out one batter per inning has fielders who help get the other two.  

So, in fact, this statistic is not fielding independent at all, despite the label its creators put on it. Do the results of a pitchers fielders actually change the pitcher's FIP? Lets look at two scenarios where a pitcher faces 9 batters:

Scenario one:

groundball hit, groundball  hit, groundball hit,

strikeout, walk, walk, strikeout, home run, strikeout.

In this scenario his FIP is 13+6-6/1 for 13.0 FIP

Scenario 2:

groundball out, groundball out, groundball out,

strikeout, walk, walk, strikeout, home run, strikeout.

In this scenario his FIP is 13+6-6/2 for a 6.5 FIP

If the fielders catch those groundballs and turn them into outs, they cut the pitcher's FIP in half. 

Is FIP really "fielding independent"? Not hardly. But you wouldn't know it from its name or how it is used around the internet.


David84 said...

Hah! Nice post, I must admit grudgingly. Not sure what to make of your point, but I think it's a good one. I've been wondering about FIP quite a bit recently myself; I think this is a good point about it.

Scott Alexander Gabriel said...

Good point, but couldn't this problem happily be solved by using some fraction of batters faced (plate appearances) instead of innings pitched?

TT said...

Yes, it could be solved simply by using batters faced. But the results would be considerably different. In the example I used, the two pitchers would have the same FIP, but one would have given up 6 earned runs, the other only 3.

My guess is that using BFP(batters faced by pitcher), the conclusion of most people would be that FIP is not very useful. It tells you very little, if anything, about how effective a pitcher is or will be.

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