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Is Slugging Percentage Relevant?


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#1
SpartanIlliniCub

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We all know that a home run is better than a base hit.  A double and triple are better than a base hit, too.  And players who can hit for extra bases or hit balls out of the park consistently are generally thought to be better and more valuable players than singles hitters.  But how much more valuable are they?

 

The stat "slugging percentage" is supposed to help quantify not only a player's batting average, but how often they hit extra base hits.  You calculate slugging percentage by adding (1B + 2x2B + 3x3B + 4xHR)  and dividing by total at-bats.  So extra base hits help inflate a player's slugging percentage more than just hitting singles.

 

For example, Kelly Kretschman of the USSSA Pride currently has a .489 batting average but a .804 slugging percentage because she hits a fair amount of extra base hits and home runs.  Seventeen of her 45 hits this season have been doubles or better.

 

Her teammate Hallie WIlson has a .324 batting average and only a .380 slugging percentage, because only 5 of her 35 hits have been doubles or better.

 

Sabremetricians have long touted slugging percentage as a better way to measure the value of a player than batting average, because batting average does not take into account a player's power numbers.  Should we ditch batting average and switch to slugging percentage?

 

I expect that slugging percentage will have a much higher correlation to win percentage than mere batting average.  Teams with the highest power numbers should win more games, right? 

 

To test this theory, I compared the batting averages and slugging percentages of the top 100 of NCAA teams to their win percentage.  Correlations are measured on a scale of 0 to 1; 0 means no correlation and 1 means a perfect correlation.  What I found when I measured these numbers surprised me:

 

oEGjWJz.png

 

I expected a much higher correlation between slugging percentage and win percentage, but the truth is it was barely higher than the correlation between batting average and win percentage.  The correlation is 0.525 for batting average and 0.612 for slugging percentage.  The difference is only .087 of a percentage point, or a 16% difference. 

 

The data indicates that, while power is a little more important than just getting a hit, it is not as important as you might think.  The ability to make solid contact and find gaps in the defense is what is really important, not how many bases the hit results in. 

 

So batting average still has a prominent place among the stats we use to judge our best hitters.  It is not time to abandon batting average for slugging percentage quite yet.

 

And for all you young hitters out there, stop swinging for the fences! Look at the data and discover that getting the ball in play is what counts—finding a place for it to drop on the field is basically as important as hitting the ball hard! 



#2
SpartanIlliniCub

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I wrote the article above about the difference between batting average and slugging percentage almost a week ago, but it still sticks with me.  Over the past week I thought about the results constantly and refused to believe my own numbers.  It seemed crazy to me that there would be so little of a difference between batting average and slugging percentage when compared with win percentage.  Slugging percentage is one of the crown jewel statistics of sabermetricians who believe baseball and softball can be analyzed and predicted by stats.  Those with high slugging percentage are supposed to be the most valuable members of a team.  Big hits drive runs across the plate.  Yet my numbers from the prior article show edthere isn't much difference between a single and an extra base hit in terms of winning games.

 

Then it hit me.  I compared batting average and slugging percentage against win percentage, when I should have compared it to runs scored.  There are so many variables in winning games beyond batting average and slugging percentage.  What if the team has a great offense but terrible pitching? Then no matter how high the slugging percentage the win % will still be low and it will throw off my numbers.  That must explain why slugging percentage wasn't much higher than batting average.  If I instead compare batting average and slugging percentage to win percentage the universe will correct itself and show that slugging percentage really matters.  To find out once and for all let's go to the numbers!

 

UnhyDhD.png

 

For this table I took the top 150 teams in terms of slugging percentage and batting average and compared that to the average runs per game of each team.  The table above only shows the top 32 teams, but I had a data set of 150 teams.  What I found from the data was shocking and disappointing.  A 1.0 correlation is a perfect correlation and a 0.0 correlation is no correlation.  The closer to 1.0 the stronger the correlation between the two numbers.

 

I want to believe so badly that extra base hits and home runs matter, but the data does not support that.  When I compared batting average and slugging percentage to runs scored the correlations were even closer than when I compared it to win percentage.  Batting average had a 0.77 correlation to runs per game and slugging percentage had a 0.83 correlation to runs per game.  These two correlations are only 0.06 percentage point apart and only 8% apart. 

 

Extra base hits and home runs are such an exciting part of softball and always seem to help push runs across, but the truth is that what really matters is that you get a hit, and not how far you hit it or how many bases you are able to snag before they get the ball to the infield. 

 

That means a team of players that hit for a high average would be better than a team with mediocre average but high power numbers.  When I first started playing little league baseball the coach asked us what the best hit in baseball was. I said the home run, but he told me I was wrong--the best hit in baseball is a base hit.  I thought it was crazy, but it turns out he was right all along.



#3
MammaZord

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This is really interesting analysis. I totally agree with the conclusions you came to. First, that wins depend on a lot more than just hits; so comparing average and slugging to runs was the better comparison. Also, I like the notion that batters should not be just swinging for the fences; getting on base (and more importantly, not giving up an out) should be their first goal. The numbers for your second analysis make perfect sense for me. Hits and slugging are obviously closely correlated to runs scored, and slugging is a little bit tighter than average. 

 

I agree that sabermetrics offer great insight into how to be successful in softball and baseball. The straightforward numbers do not always show the full story though, and it might take some deep digging to really understand how teams get wins. For instance- some teams may have one hitter with a great slugging percentage that brings up the overall team average. However, her great slugging does not mean much if her teammates can not hit: no runs for her bring in; no one to hit her in. So, in order to utilize sabermetrics, you have to go deep into the numbers. 



#4
CatOsterFan

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I read the book Moneyball by Michael Lewis (the one they made a movie out of with Brad Pitt and Jonah Hill) and the conclusion the whiz kids of the Oakland A's came to was that the most important stat was whether or not you contributed an out.  Whether it's a walk, a home run, hit by pitch, or walk, they are all pretty much weighted equally.  That is why the Oakland A's in the 90's tried so hard to get hitters to take more walks and, therefore, less outs.






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