MLB Research Data - Statcast Correlations

Descriptive	Descriptive correlations are the “R” value from a standard Pearson correlation between each of the two stats, accrued by a player during the same year. Players must have accrued at least 300 plate appearances in a given year (or 10 stolen base attempts, for SB) to be included in the analysis
Projected	Predictive correlations are the “R” value from a standard Pearson correlation between a player’s Statcast stat in one year and his traditional stat the following year. Players must have accrued at least 300 plate appearances in both years (or 10 stolen base attempts, for SB) to be included in the analysis
Barrel%	The rate of barrels, as per the official Statcast definition: “batted-ball events whose comparable hit types (in terms of exit velocity and launch angle) have led to a minimum .500 batting average and 1.500 slugging percentage since Statcast was implemented Major League wide in 2015.”
Launch Angle (Average)	“How high, in degrees, a ball was hit by a batter,” as per the official Statcast definition. The “(Average)” version of Launch Angle is, as the name suggests, the average launch angle of all balls a hitter contacted and Statcast recorded data on
Launch Angle (Sweet Spot)	The average launch angle of a hitter’s batted balls that are within the top one-third of his hardest struck batted balls. Coined by Tom Tango, Senior Data Architect for MLBAM: “The idea being that the harder you hit the ball, the more likely you ‘got all of it’, and so, the launch angle was your intended launch angle. You got it on the sweetspot of the bat, and so, the byproduct of that is your… Sweetspot Launch Angle.”
Launch Angle (-4 to 26%)	The percentage of balls the batter hits with a launch angle between -4 and 26 degrees. This range produces league average BABIPs over .300
Launch Angle (23 to 34%)	The percentage of balls the batter hits with a launch angle between 23 and 34 degrees. This range produces league average HR% over 20%
Launch Angle (38%+)	The percentage of balls the batter hits with a launch angle over 38 degrees. This range indicates an extreme uppercut swing, which can lead to power but also kills batting average and BABIP
Launch Angle (Standard Deviation)	The standard deviation of the launch angle of all of a hitter’s batted balls – i.e. how tightly clustered a hitter’s launch angles are (the smaller the number, the tighter). Alex Chamberlain originally led research into this stat as a proxy for bat control and contact skills. It is one of the best descriptive indicators of BABIP and a good predictive one
Exit Velocity (Average)	“How fast, in miles per hour, a ball was hit by a batter,” as per the official Statcast definition. The “(Average)” version of Exit Velocity is, as the name suggests, the average exit velocity of all balls a hitter contacted and Statcast recorded data on
Exit Velocity (Max)	The exit velocity of the hardest ball the player hit
Exit Velocity (Top 5%)	The average exit velocity of the top 5% of the hardest balls the player hit
Exit Velocity (Next 20%)	The average exit velocity of the top 5% through 25% of the hardest balls the player hit (note this does not include balls in the top 5%)
Exit Velocity (Flyballs)	The average exit velocity on balls labeled by MLBAM as a flyball
Exit Velocity (100+ mph In Air%)	The percentage of balls hit into the air by a batter that have an exit velocity of 100 mph or greater
Spray Score	Created by Derek Carty, it is a measure of how evenly a player hits the ball to all fields (i.e. sprays the ball). It is calculated by taking the absolute value of the percentage of balls hit to each field (pull, center, opposite) minus .33, and adding up the values for all three fields. A hitter who hits balls evenly to all fields (i.e. 33% to each field) will have a Spray Score of 0. A hitter who hits all balls to one field will have a Spray Score of 1.33. The lower Spray Score is a good indicator of contact ability
Sprint Speed	“A measurement of a player's top running speed, expressed in ‘feet per second in a player's fastest one-second window’,” as per the official Statcast definition
wOBA	Weighted On-Base Average. Created by Tom Tango, the best measure of a player’s offensive contribution to run-scoring
HR%	The rate of home runs per contacted ball
BABIP	Batting Average on Balls in Play. In other words, the percentage of non-home runs balls that become hits
ISO	Isolated Slugging. Slugging Percentage minus Batting Average, a commonly used measure of a player’s power
BA	Batting Average
SB%	Stolen Base Success Rate. The rate of successful stolen bases per attempted stolen base. The inverse of caught stealing percentage
SBA%	Stolen Base Attempt Rate. The rate of attempted stolen bases per on-base opportunity to steal a base

Note: Statcast stats are calculated live by in-ballpark cameras and radar. These occasionally fail to record data on certain batted balls. All data and projections displayed at EV that rely on Statcast data identify these missed balls and estimate what they should have been. Internal tests showed this to be slightly more accurate than either ignoring the missing data or using MLB's

Descriptive	Descriptive correlations are the “R” value from a standard Pearson correlation between each of the two stats, accrued by a player during the same year. Players must have accrued at least 300 plate appearances in a given year (or 10 stolen base attempts, for SB) to be included in the analysis
Projected	Predictive correlations are the “R” value from a standard Pearson correlation between a player’s Statcast stat in one year and his traditional stat the following year. Players must have accrued at least 300 plate appearances in both years (or 10 stolen base attempts, for SB) to be included in the analysis
Barrel%	The rate of barrels, as per the official Statcast definition: “batted-ball events whose comparable hit types (in terms of exit velocity and launch angle) have led to a minimum .500 batting average and 1.500 slugging percentage since Statcast was implemented Major League wide in 2015.”
Launch Angle (Average)	“How high, in degrees, a ball was hit by a batter,” as per the official Statcast definition. The “(Average)” version of Launch Angle is, as the name suggests, the average launch angle of all balls a hitter contacted and Statcast recorded data on
Launch Angle (Sweet Spot)	The average launch angle of a hitter’s batted balls that are within the top one-third of his hardest struck batted balls. Coined by Tom Tango, Senior Data Architect for MLBAM: “The idea being that the harder you hit the ball, the more likely you ‘got all of it’, and so, the launch angle was your intended launch angle. You got it on the sweetspot of the bat, and so, the byproduct of that is your… Sweetspot Launch Angle.”
Launch Angle (-4 to 26%)	The percentage of balls the batter hits with a launch angle between -4 and 26 degrees. This range produces league average BABIPs over .300
Launch Angle (23 to 34%)	The percentage of balls the batter hits with a launch angle between 23 and 34 degrees. This range produces league average HR% over 20%
Launch Angle (38%+)	The percentage of balls the batter hits with a launch angle over 38 degrees. This range indicates an extreme uppercut swing, which can lead to power but also kills batting average and BABIP
Launch Angle (Standard Deviation)	The standard deviation of the launch angle of all of a hitter’s batted balls – i.e. how tightly clustered a hitter’s launch angles are (the smaller the number, the tighter). Alex Chamberlain originally led research into this stat as a proxy for bat control and contact skills. It is one of the best descriptive indicators of BABIP and a good predictive one
Exit Velocity (Average)	“How fast, in miles per hour, a ball was hit by a batter,” as per the official Statcast definition. The “(Average)” version of Exit Velocity is, as the name suggests, the average exit velocity of all balls a hitter contacted and Statcast recorded data on
Exit Velocity (Max)	The exit velocity of the hardest ball the player hit
Exit Velocity (Top 5%)	The average exit velocity of the top 5% of the hardest balls the player hit
Exit Velocity (Next 20%)	The average exit velocity of the top 5% through 25% of the hardest balls the player hit (note this does not include balls in the top 5%)
Exit Velocity (Flyballs)	The average exit velocity on balls labeled by MLBAM as a flyball
Exit Velocity (100+ mph In Air%)	The percentage of balls hit into the air by a batter that have an exit velocity of 100 mph or greater
Spray Score	Created by Derek Carty, it is a measure of how evenly a player hits the ball to all fields (i.e. sprays the ball). It is calculated by taking the absolute value of the percentage of balls hit to each field (pull, center, opposite) minus .33, and adding up the values for all three fields. A hitter who hits balls evenly to all fields (i.e. 33% to each field) will have a Spray Score of 0. A hitter who hits all balls to one field will have a Spray Score of 1.33. The lower Spray Score is a good indicator of contact ability
Sprint Speed	“A measurement of a player's top running speed, expressed in ‘feet per second in a player's fastest one-second window’,” as per the official Statcast definition
wOBA	Weighted On-Base Average. Created by Tom Tango, the best measure of a player’s offensive contribution to run-scoring
HR%	The rate of home runs per contacted ball
BABIP	Batting Average on Balls in Play. In other words, the percentage of non-home runs balls that become hits
ISO	Isolated Slugging. Slugging Percentage minus Batting Average, a commonly used measure of a player’s power
BA	Batting Average
SB%	Stolen Base Success Rate. The rate of successful stolen bases per attempted stolen base. The inverse of caught stealing percentage
SBA%	Stolen Base Attempt Rate. The rate of attempted stolen bases per on-base opportunity to steal a base