BABIP’s relationship to hitters

Realistically, the (minimal) effect you’re seeing is largely due to a sampling concern - the more BIP you have, the closer to the mean your BABIP is likely to be. (This is why regression to the mean works - the more observations you have, the likelihood that a result is closer to the mean increases.)

Another possibility is that your AB threshold is a little low.  BABIP can fluctuate a lot with a smaller sample size (think about Ramon Vazquez’ incredible start last year).  What do the numbers look like if you use 400 or 500 AB, so you only include players who played a full season?

A good effort of what seems like a reasonable hypothesis.

My guess is that the reason no significant relationship appeared was that, for even the low end of the BIP scale, there are enough over the course of a season to give an accurate figure (which would not be improved a lot by adding another 100 or so BIP).  But, I could be mistaken.

From my experience as a fantasy team manager, the variability of BABIP tends to be valuable over shorter time frames when sample size is still small (e.g. early in-season, when a player is clearly under average in terms of BABIP, which makes him a good trade target).  That is when preying on disenchanted owners can be highly profitable.