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# Do plate discipline statistics correlate with strikeout and walk percentages?

Come play two truths and a lie with plate discipline statistics!

Remember back when you were in grade school and the teacher had time to kill? The teacher had finished teaching the daily lesson early, and the class had some free time at the end of the day. The class, in general, just wanted a relaxing way to finish out the day.

Now come back to today. You have a job that you work at every day. Your boss might not be as nice as your teacher once was, i.e., it’s tougher to play games that can help finish out the day. But it’s Friday! Let’s celebrate Friday by playing a game, just like you would if you were in school. An easy-going game of two truths and a lie—but with a Beyond the Box Score-style spin.

Recently I have been combing over some of the PitchF/X plate discipline data, such as swing and contact percentages, that FanGraphs offers, which I then decided to compare to strikeout and walk percentages. Wondering if there was any relationship between the two, I plotted every qualified players’ total since 2010 against each other and added a simple linear trendline to get my answer.

This attempt to find a correlation is what will drive our game. We will use the game to find out if there is or isn’t a correlation, and what it might mean. Here are the three statements:

1. The more contact a player has the less he strikes out
2. The more pitches a player chases the higher likelihood he strikes out.
3. There is little-to-no relationship between Pitchf/x plate discipline statistics and strikeout or walk percentages.

### The more contact a player has the less he strikes out

This one should be pretty straightforward. Of course the more contact a player makes the less likely that same player is to strikeout. That’s just common sense. If a player puts the ball in play, then there’s absolutely no way for him to strikeout. However, if a player does not have a high likelihood of making contact, then that same player will strike out more often.

Obviously this is one of the two truths, as it shouldn’t really be a surprise to many. But in any good game, there always has to be that "Duh!" truth that doesn’t really shock anyone. Players like Juan Pierre, Marco Scutaro, and Ben Revere have posted seasons in which they had extremely high amounts of contact and struck out very little. As for the other side of the coin, players like Chris Carter, Matt Reynolds, and Adam Dunn are examples of players that have extremely high strikeout percentages and make contact with the ball an unimpressive amount of the time.

### The more pitches a player chases the higher likelihood he will strike out

We have found our lie! That is a correlation of 0.0001, otherwise known as no correlation. This is surprising because typically you would think that if a player swings at bad pitches a lot then he is more likely to strike out. It appears that is not the case. In fact, out of the 12 comparisons this one had the lowest correlation.

Players like Victor Martinez, Adrian Beltre, and Jose Altuve have never been afraid to swing at a pitch outside the strike zone and have also managed a relatively low strikeout percentage. Vladimir Guerrero was basically the epitome of this phenomenon. Dan Uggla, Josh Willingham, and Rickie Weeks are examples of guys who have a high percentage of strikeouts yet do not chase the ball outside the strike zone as much as you might think.

### There is little-to-no relationship between PitchF/X plate discipline statistics and strikeout or walk percentages.

Now that the lie has been exposed, this must be true—and it is. The weirdest thing about all of the plate discipline statistics is that the only real correlation was between the contact percentage and strikeout percentage. This means that the only thing that plate discipline statistics tell us is that the more contact you make, the less you strikeout. See for yourself:

 O-Swing% Z-Swing% Swing% O-Contact% Z-Contact% Contact% K% .0001 .042 .0039 .6999 .6923 .7945 BB% .4016 .0504 .3279 .0705 .1026 .0575

That is the R-squared of each of the six plate discipline stats compared to strikeout and walk rates, meaning the same thing as I have said previously—there is little to no relationship between the two. There’s a plethora of other reasons why there isn’t a strong relationship between the two. Some players are OK with striking out but want to make sure they don’t miss their pitch when they get it. Other players are free swingers, swinging at anything they like. It is likely because players take vastly different approaches at the plate—an openness or reluctance to swing at a certain pitch in a certain count—that attributes to the wide variety of hitters in today’s game.

So as we bring to a close this game of two truths and a lie and you return to your work, here’s what we can conclude. As FanGraphs describes, the main purpose of these stats is to "tell us how often a hitter swings and makes contact with certain kinds of pitches or how often a pitcher induces swings or contact on certain kinds of pitches". However, it should come as a surprise that not many of these stats mean that a player is more or less likely to strike out or walk.

. . .

Shawn Brody is a contributor for Beyond the Box Score, as well as a sophomore pitcher at Howard Payne University majoring in Business Management. He has the current misfortune of being a Red Sox fan. If you would like to get a hold of him, please feel free to email him at Shawnbrody9@gmail.com or follow him on Twitter @ShawnBrody.