YOU'RE ACTUALLY SAYING "hmm, that road avg. doesn't look quite right, let's arbitrarily just take away 15% of his hits" Except it's not arbitrary at all. It's specifically aimed at correcting an anomaly in the data. That's the whole point, actually... trying to see what Headley would be if he was neither lucky nor unlucky. It may be aimed at correcting it, but you're way off because you either didn't use a specific methodology or just failed to explain it. Therefore, yes, it's completely arbitrary. How did you come up with the numbers? How do you know Headley isn't a guy who can sustain a .340-.350 babip in a relatively neutral park?