QUOTE(Gene Honda Civic @ Oct 15, 2005 -> 07:53 AM)
Your "defence impact ratio" got me thinking...
So I compared each teams DER [(Defensive Efficiency ratio) which is simply the % of Balls in play converted into outs] to their ERA
I got a correlation of -.839 -- As the DER comes down (less Balls in play converted into outs) the ERA goes up. Obviously, this is to be expected, but .839 is not all that strong.
Especially when you consider that Team OBP correlates to Runs scored at about .92 and Team OPS correlates to runs scored at about .95 *** Those correlations are from memory, so they may not be 100% accurate, but they're close.