Four years is a weak basis for establishing a strong correlation. His career numbers tend to show that he hits only a tick better with RISP. It's not too weak when he's only been the player that he is for four years. Over the last four years, he's been a completely different player than what he was with Pittsburgh, I think that's pretty obvious. As for your second point... only a tick? With RISP, his OBP is 40 points higher and his SLG is 50 points higher. That's not exactly a tick, that's pretty significant. As Ender just said, 4 years isn't a lot. Not when you have over a century worth of baseball. I'm not talking about players in general though, I'm talking about one player. So yes, when you have one player who's been at the same level for four years, it's a perfectly fine sample size. You don't need to look at 100 years worth of data to find something out about one guy. There you go, Jacque. Edit: Jacque? Wow, not sure where that came from.