Comments on: Pitcher Win Value Correlations

By: Tom

Tom — Sat, 24 Jan 2009 21:46:12 +0000

Hi Dave, I’ve really enjoyed your work here and at USSM. Been reading for about a year but this is my first time commenting. Thanks for explaining FIP and Win Values, a great set of posts.

I was wondering when you were going to get to predictive power of FIP generated win values on future performance – the crucial question. But showing that past FIP correlates to future FIP is sort of skirting the question. To be valuable, win values must predict future, well, wins. Of course Wins (with a capital W) are full of noise and only loosely correlated to performance. But for comparing across different methods of Win values, that’s OK, especially with large sample sizes.

I think it would be very powerful to show a positive correlation for something like the following (for starting pitchers): FIP on the Y-axis and # of games started won divided by teams total wins on the X-axis. Then ask does FIP show a stronger correlation then other measures of performance, such as ERA or K/9.

Something like this needs to be done (probably already has?) to show that Win values actually lead to wins for the team! Would love to hear your thoughts.

By: Nathan

Nathan — Thu, 22 Jan 2009 04:02:11 +0000

Is it just me, or does the 10 IP cutoff for the sample group seem very low. I would think that you would want it quite a bit higher as that amount of work would not prove to be statistically significant. It would also be interesting to see the results if the starters are separated from the relievers.

By: philosofool

philosofool — Thu, 22 Jan 2009 00:53:54 +0000

Dave,

Did you separate relievers from starters when determining these correlations? If not, I wonder whether the strength of the correlation has to do just with play time correlations between these two roles. It seems odd to me that play time + FIP (the ingredients in win values) should exceed FIP alone in reliability.

By: Ben

Ben — Wed, 21 Jan 2009 23:44:16 +0000

I am curious about FIP y-t-y correlation as well…

By: Sky

Sky — Wed, 21 Jan 2009 23:05:22 +0000

What’s y-t-y correlation for FIP on its own? How about IP?

By: Tony

Tony — Wed, 21 Jan 2009 23:01:29 +0000

I was going to say the exact same thing, Graham.

By: Graham

Graham — Wed, 21 Jan 2009 21:47:36 +0000

I need to brush up on my correlation inputs a bit but isn’t 10IP a really small amount to use?

By: David Appelman

David Appelman — Wed, 21 Jan 2009 19:31:30 +0000

Those correlations look quite good to me. I don’t think you’re going to get things a whole lot better on y-t-y correlations for one single stat on a pitcher’s overall value.

Personally, I think the only thing worth adding into the win values at some point is GB%.