## K% and GB% standard deviations and their effects on performance

A guy with strikeout and ground ball skills. He's made his dent in history. - USA TODAY Sports

If we can control for one variable, can we discover which affects performance more?

In this installment of my standard deviation starting pitcher series, I will be examining the relationship between K% and GB% and how those two variables affect performance. The methodology is basically the same as before; since batted balls are included, the years included in this analysis are 2002-2013. In addition, only starting pitchers who have at least 70 batters faced for a stable K% and 70 balls in play (GB+FB+LD) for a stable GB% are included. I have again chosen RA9-WAR as the performance metric for each group.

 GB% -2 -1 0-1 0+1 1 2 RA9-WAR K% -2 N/A N/A -1.1 N/A -0.6 -0.7 -0.7 -1 N/A -0.5 -0.1 -0.1 0.2 1 -0.1 0-1 0 0.3 0.4 0.7 1.1 1.9 0.7 0+1 0.6 1.2 1.4 2 2.7 2.8 1.7 1 1.1 1.9 2.7 4.1 3.3 5.8 3 2 N/A 2.4 5.5 4.5 3.7 N/A 4.8 RA9-WAR 0.5 0.9 1.1 1.4 1.6 2.3

Across the top of the table are the GB% standard deviation groups, and going down the table are the K% standard deviation groups. -2 means at least two standard deviations below the middle, -1 means at least one standard deviation below the middle, 0-1 means between 0 and 1 standard deviations below the middle, etc. The RA9-WAR values shown in the far right column are the median RA9-WAR values for each K% group regardless of GB%, and the RA9-WAR values shown in the bottom row are the median RA9-WAR values for each GB% group regardless of K%. For example, the median RA9-WAR for all pitchers who were at least 2 standard deviations above the middle K% is 4.8. N/A means there were no pitchers in that group.

Compared to the K% and BB% relationship, the relationship between K% and GB% is not quite as clear. It seems that at the low end of the K% spectrum, having a higher GB% can help overcome a low K%. For example, the group whose K% is between 0 and 1 standard deviations below the middle and GB% is 2 standard deviations above the middle, abbreviated (0-1,2), has an RA9-WAR value of 1.9. The RA9-WAR value for the K% of this group is 0.7, so having a higher GB% aided that group's performance. The lower K% does bring down that group's performance compared to all pitchers who were at least 2 standard deviations above the middle in GB%, though, as that group's median RA9-WAR was 2.3.

On the higher K% side of things, there were mixed results. Those pitchers in group (1,2) had a median of 5.8 RA9-WAR, though only six pitchers are in that group. The combination of high K% and high GB% elevated the performance of that group above the median RA9-WAR value for either K% alone or GB% alone. However, group (1,1) had a median RA9-WAR value of 3.3, which does not follow the general trend of increasing RA9-WAR with increasing GB% and wasn't far from the overall K% +1 group median RA9-WAR value of 3. There were 43 pitchers in that group, so sample size doesn't appear to be the cause.

In general, having a higher GB% can help elevate the performance of a pitcher regardless of K%, but this relationship is not as clear as K%. Having a higher K% can overcome a low GB%, but there are situations in which a lower GB% can be a good thing (see the Oakland Athletics). It appears that the effect of K% is stronger than the effect of GB%, but having a higher GB% is a good way to extract value out of cheaper pitchers whose K% is low.

. . .

All statistics courtesy of FanGraphs.

Kevin Ruprecht is a contributor to Beyond the Box Score. He also writes at Royal Stats for Everyone. You can follow him on Twitter at @KevinRuprecht.

More from Beyond the Box Score

## Trending Discussions

Log In Sign Up

forgot?
Log In Sign Up

### Please choose a new SB Nation username and password

As part of the new SB Nation launch, prior users will need to choose a permanent username, along with a new password.

Your username will be used to login to SB Nation going forward.

I already have a Vox Media account!

### Verify Vox Media account

Please login to your Vox Media account. This account will be linked to your previously existing Eater account.

### Please choose a new SB Nation username and password

As part of the new SB Nation launch, prior MT authors will need to choose a new username and password.

Your username will be used to login to SB Nation going forward.

### Forgot password?

We'll email you a reset link.

If you signed up using a 3rd party account like Facebook or Twitter, please login with it instead.

### Forgot password?

Try another email?

### Almost done,

By becoming a registered user, you are also agreeing to our Terms and confirming that you have read our Privacy Policy.

### Join Beyond the Box Score

You must be a member of Beyond the Box Score to participate.

We have our own Community Guidelines at Beyond the Box Score. You should read them.

### Join Beyond the Box Score

You must be a member of Beyond the Box Score to participate.

We have our own Community Guidelines at Beyond the Box Score. You should read them.

### Great!

Choose an available username to complete sign up.

In order to provide our users with a better overall experience, we ask for more information from Facebook when using it to login so that we can learn more about our audience and provide you with the best possible experience. We do not store specific user data and the sharing of it is not required to login with Facebook.