Hey all, I originally posted this over at Purple Row. Pardon me if it seems somewhat simplistic or a little "audience specific" or something but I figured hey it might have some interesting stuff and can only do more good than harm. Enjoy.
Hey everyone, after reading RockiesMagicNumber's post about Chris Iannetta, it got me thinking about how much BABIP is correlated with other statistics. Specifically, in the post he discusses how Iannetta's linedrive rate is uncharacteristically low and that's contributing towards his low BABIP. He mentions it in that post but BABIP is Batting Average on Balls In Play. I guess you could call it a "sabermetric stat" but honestly it's just batting average without counting strike outs and home runs. It also gets referred to as an index of luck. Batters tend to have a BABIP around .300. Power hitters and speedy hitters tend to average a BABIP higher than that. (Garrett Atkins, Ian Stewart, and Chris Iannetta are all currently sporting BABIPs of .250~)
Anyway, I wanted to see just how correlated linedrive rate and BABIP are. I got the numbers from fangraphs (with the import to excel feature - seriously, how friggin cool is that website?) for the 164 batters who qualify and ran some correlations.
Here's the output:
None of this stuff is too profound, and there's a good chance it was already available somewhere on the net, but what the hell, it's an off day and I needed a good excuse to mess around with SPSS.
So in the end, BABIP and line drive % have a correlation (r) of .489. To get the r-squared statistic (r^2), you take the correlation coefficient r (.489), and square it (straightforward enough). The r^2 stat for this is .239. What this basically means (and please correct me if I'm wrong), is that 24% of the variation in BABIP is attributable to line drive rate.
For those of you who don't know, correlations have a range of -1.000 through 1.000. The further you are away from the midpoint 0, the stronger the correlation.
So some other things in that table - BABIP and Fly ball percentage have an even stronger correlation than BABIP and linedrive rate (although only by .001). However, whereas an increase in linedrive rate leads to an increase in BABIP, an increase in flyball rate leads to a decrease in BABIP - Iannetta's increase in fly balls this year may also be why his BABIP is down.
Unsurprisingly, Flyball rate and groundball rate have a -.931 correlation.
P.S. Ironically, Chris Iannetta's numbers did not contribute towards this "study" as he does not have enough at bats to qualify.