xBA versus Projected BA

[Yerout]

I probably missed this somewhere but I'm trying to figure out why there is a difference in the BA projections in the Forecaster compared with the xBA for the same player. What's the difference?

[helloneumn]

From the glossary, the definition of xBA (Expected Batting Average) is:

xCT% * [xH1% + xH2%]

where

xH1% = GB% * [0.0004 PX + 0.062 ln(SX)]

+ LD% * [0.93 - 0.086 ln(SX)]

+ FB% * 0.12

and

xH2% = FB% * [0.0013 PX - 0.0002 SX - 0.057]

+ GB% * [0.0006 PX]

A hitter's batting average as calculated by multiplying the percentage of balls put in play (contact rate) by the chance that a ball in play falls for a hit. The likelihood that a ball in play falls for a hit is a product of the speed of the ball and distance it is hit (PX), the speed of the batter (SX), and distribution of ground balls, fly balls, and line drives. We further split it out by non-homerun hit rate (xH1%) and homerun hit rate (xH2%). BENCHMARKS: In general, xBA should approximate batting average fairly closely. Those hitters who have large variances between the two gauges are candidates for further analysis.

Oh, and welcome to the Boards

[Michael@HQ]

I agree, it's a bit confusing.

One thing to keep in mind is that xBA is a model that fits most players but that the projections peek at actual BA too to see if a guy has a history of outperforming xBA. Ichiro Suzuki is the most obvious example (although his H% still varies pretty wildly). Still, that doesn't totally explain it.

[Yerout]

Thanks - the fog is lifting.

[tedpower]

on a similar note is it safe to assume that the difference between the projected expected batting average and the projected batting average based on ballpark factors?

an example would be Eric Chavez with a projected xBA of .268 but a projected BA of .255 or Rajah Davis with a projected xBA of .241 but a projected BA of .263.

thanks in advance,
Joe

[RAY@HQ]

Yeah, that's certainly going to be a factor, ted.