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You’ll often hear or read that match-ups are favorable since the hitter or pitcher is playing at home. Today we’re going to focus on hitters and demonstrate the extent of home-field advantage. Tomorrow we’ll investigate pitchers.

From a practical view, we care most how playing at home influences the hitting stats to which most stats assign points. As such, we’ll look at the home versus away numbers of wOBA, K%, BB%, HR% and runs scored. The splits from 2011 through 2013 will be included as well as what has occurred to date in the current campaign.

The goal is to determine exactly how much to adjust the daily projection based on the home/away aspect of a player’s match-up. In fact, the results about to be presented are incorporated into the Fantasy Alarm Projection and Pricing tool.

Here’ the pertinent data.

wOBA 2014 2013 2012 2011
home 0.320 0.318 0.322 0.322
away 0.307 0.310 0.308 0.310
MLB 0.314 0.314 0.315 0.316
K% 2014 2013 2012 2011
home 19.8% 19.3% 19.3% 18.3%
away 20.8% 20.4% 20.3% 19.0%
MLB 20.3% 19.9% 19.8% 18.6%
BB% 2014 2013 2012 2011
home 8.2% 8.3% 8.4% 8.4%
away 8.1% 7.6% 7.6% 7.8%
MLB 8.2% 7.9% 8.0% 8.1%
HR% 2014 2013 2012 2011
home 2.49% 2.55% 2.75% 2.54%
away 2.27% 2.50% 2.61% 2.38%
MLB 2.38% 2.52% 2.68% 2.46%
runs 2014 2013 2012 2011
home 3190 10185 10709 10447
away 3154 10070 10308 10361
MLB 6344 20255 21017 20808

For those not familiar with the nomenclature, strikeout (K), walk (BB) and home run (HR) percent are all computed per PLATE APPEARANCE. As can be readily observed, each statistic is better at home.

Of particular interest is runs. While it stands to reason improved skills lead to more runs, keep in mind that when the home team is winning they don’t hit in the ninth. There’s a chance fewer innings could result in fewer total runs but as can be witnessed, clubs still average more runs at home. The offshoot is the daily runs and RBI projection should be adjusted along with those associated with the above skills.

Here’s a chart showing the average percent improvement for home games and decrease for road tilts from 2011-2013 for each statistic as compared to the overall total.

  wOBA K% BB% HR% runs
Home 1.8% -2.4% 4.6% 2.3% 1.0%
Away -1.8% 2.4% -4.2% -2.2% -1.0%

These are the numbers specifically incorporated into the Projection and Pricing tool. As an example, leaving aside park factors for a moment, a batter’s neutral baseline strikeout projection is decreased 2.4 percent for home games while their neutral homer baseline is decreased by 2.2 percent on the road.

At this point you may be wondering if there is a similar relationship for player’s home-away splits as there are for handedness. As was discussed last time, players with sufficient experience can own their versus lefty and righty splits while players with a limited track record need to have their numbers regressed to the league norm. Home-away is a little different as the park contributes to a player’s splits. The assumption made here is each player is influenced in concert with the league norm before factoring in the park effect.

For those curious how the sausage is made, as alluded to earlier, each hitter’s rest-of-season projection is adjusted to be park-neutral. The above home-away adjustments are made followed by an adjustment specific to the park. The final step is an adjustment based on the opposing pitcher which is a topic to be broached at a future date.

The end-result is a per plate appearance projection for each pertinent stat. The tool then uses each site’s scoring system to generate projected points for each hitter.

Next time we’ll take a look at the home-away effect for pitchers. Under investigation will be strikeouts, walks, runs allowed, win potential, save potential and innings pitched.

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