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Monday, January 09, 2012
Correlation of pitcher metrics: FIP strikes again
You have to love the huge amount of effort and great presentation.
So, what correlates best with Year 2 ERA? Basically, K/PA! That’s right, just knowing strikeouts per PA is as good as just about everything else. FIP is a smidge better. So, including BB and HR barely moved the needle. In your first, just barely ahead of FIP, is tERA, which I think is the Stat Corner stat that used batted ball characteristics.
There are a couple of things in there to note:
1. There is a selection bias issue, since you needed to have 162 IP in both samples.
2. There is no reason to have counting stats correlated to rate stats. There is both ER and ERA in the correlation. We don’t need the ER information as a counting stat. We’re saved here, since everyone has close to the same number of innings 162 to 250 or something. But, it’s luck that the results came out as they did.
In terms of what correlates with ERA- in year2 (meaning ERA adjusted for league and park), we have: FIP- in year1 (meaning FIP adjusted for league and park). SIERA did as well as FIP (meaning unadjusted FIP).
When it comes down to it, it’s extremely difficult to do better than FIP, no matter how hard you try.