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To catch everyone up, the idea is that a hit (or out) happened. And our job is simply to explain how that hit (or out) happened. It's not 35% of a hit or 72% of a hit or even 1% or 99%. It's exactly 100% (if it was a hit) or 0% (if it was an out). And so, what makes up that 100% (or 0%)?</p> <ul><li>We have making contact. Just making contact will lead to a hit about 33% of the time. </li><li> We have the launch speed. That can bring that number as high as 80% with maximum speed or as low as 20% with minimum speed. In other words, the Layer of launch speed will be somewhere between -13% and +47% (for an average of 0% for an average batter).</li><li>How about launch angle? Well, depending on the launch speed, that can explain as high as 100% (think easy HR) or as low as 0% (think easy popup). So, the Layer of launch angle can be between -70% and +80% (for again an average of 0%).</li><li>What else can explain the hit or out? We have the carry of the ball (meaning the spin and/or wind and/or specific ball characteristics... remember every ball is as unique as a snowflake, even if it comes from the same batch).</li><li>We have the spray angle (meaning finding those gaps between fielders or clearing the fence).</li><li>We have the running speed of the batter to beat out grounders.</li><li>We have the fielding alignment on that specific play.</li><li>We have the specific fielder involved on that specific play (did they make a great play, or a terrible play, or something in-between).</li></ul> <p>Other than the unrecorded events like lights, sun, and catwalks, all of these variables comprise the totality of what can happen to a batted ball that will turn it into a basehit or an out.</p> <p>And so, that's what we do. We go thru each one of the 120,000 batted balls, and make sure that every layer is given a value so that the sum total of those layers is exactly 100% (for a basehit) or 0% (for a batted ball out). In other words, we will exactly describe each play.</p> <p><strong>WHY</strong></p> <p>Why do we do that? Well, now that we have each component perfectly described retroactively, we can use that information to ALSO predict future batted balls. Since some components are more in the control of the batter, then those components will carry more weight for predictions.</p> <p>Let's take an obvious one. Pete Crow-Armstrong makes a highlight play, earning +0.90 OAA (outs above average). If PCA is earning +0.90 OAA, then guess what, the batter is going to get -90% for the Fielder Layer in Layered Hit Probability. Remember, we are trying to explain the result (an out in this case) and so how do we get to 0% hits? Well, the batter may have gotten great contact at a great launch angle and he was probably sitting at +90% in layers, but the fielding layer was worth -90% and so that's 0% hits. That describes that play. But what about the PLAYER? Well, in that case, we likely put most of our weight on his launch speed and launch angle.</p> <p><strong>WEIGHTS</strong></p> <p>How much weight? And how about all the other layers? Well, I'm glad you asked.</p> <p>Running a correlation of current season layers to next season BACON (batting average on contact), we get an r=0.56. In contrast, the traditional xBA gives us a correlation of r=0.45. So, right away, we know we've got something value-added here.</p> <p>Let's look at it layer by layer. The first most obvious one is launch speed. At a p value of 0.0000000 (make that 39 zeroes), it's clear the Launch Speed Layer is critical. It's weight is 0.64. I don't think we need to belabour the value of launch speed.</p> <p>Launch Angle Layer is the next most important (also a p-value of 0, but this time to 7 zeroes). Its weight is 0.28.</p> <p>Batter Running Speed Layer, with a p-value of 0, and a full weight of 1.00. This one makes the most sense: the batter's running speed IS the actual description of the batter. This is unlike launch speed and launch angle which is a product of his skill, and not the skill itself. It's pretty close naturally. But it is not exact. That's why launch speed has a weight of 0.64 and not 1, and why launch angle is 0.28 and not 1.</p> <ul><li>That said, on a seasonal basis, batter by batter, the Launch Speed layer is between -9% and +14%. Taking 0.64 of that, and we can say that the Launch Speed Skill will range from -6% to +9%.</li><li>Launch Angle Layer, observed at +/-12% would establish a Launch Angle skill of -3% to +3%.</li><li>Running Speed Layer goes from -1% to +2%.</li><li>I hope this is making sense. Anyway, let's keep going. The next important layer, far behind these, is Fielding Alignment Layer, with a p-value of 0.09. Now, that is a high number, high enough that we might even suggest that Fielding Alignment has no predictive value. Its average coefficient is 0.11, but the range of possible coefficient is -.02 to +.25. It's enough for us to simply not use it at all for predictive purposes. To the extent that you want to use it: the observed range is +/-6%, and so the Fielding Alignment Skill is +/-0.6%.</li><li>After that, it's the Spray Angle Layer, at a p value of 0.22. This one is even more clear that it adds almost no value. The weight is 0.10, but it can possibly range from -0.06 to +0.25. When you see a p value that high, you are basically going to say Random Variation. The observed range is +/-5%, which means the Spray Angle Skill is +/-0.5%. But like I said, it may as well be 0.</li><li>Finally, the Carry Layer, at a p value of 0.48 is really screaming Random Variation. And with a coefficient close to 0, it's really not worth even discussing it. The observed range is +/-5%, but the skill range is 0%. In other words, this Layer as well as the Fielding Layer, is perfectly apropos for describing the PLAY and totally unusable in describing the PLAYER.</li></ul> <p>To summarize the weights and skill ranges of each:</p> <ul><li>Weight, Skill Layer, Component</li><li>0.64, -6% to +9%, Launch Speed</li><li>0.28, -3% to +3%, Launch Angle</li><li>1.00, -1% to +2%, Running Speed</li><li>0.11, -0.6% to +0.6%, Fielding Alignment</li><li>0.10, -0.5% to +0.5%, Spray Angle</li><li>0.00, 0%, Carry</li><li>0.00, 0%, Fielder</li></ul> <p>All in all, what are we most interested in, with a hit probability metric? Launch Speed, Launch Angle, and Running Speed. Which is how xBA currently exists.</p> <p>However, breaking it up into components allows us to weight each of the three separately. And so, that's how we can bring our correlation from r=0.45 using the amalgamated xBA to r=0.56 using a Layered approach.</p> <p>And yes, the individual layers will be available, batter by batter on a seasonal basis, on Savant at some point.  I don't know when.</p> <hr/> <div class="posted"> (5) <a href="http://tangotiger.com/index.php/site/comments/layered-hit-probability-breakdown#comments"> Comments </a> • 2024/10/28 • <a href="http://tangotiger.com/index.php/site/category/batted-ball"> Batted_Ball </a> </div> </div> <p> <a href="http://tangotiger.com/index.php"> << Back to main </a> </p> </div> <div class="sidebar"> </div> </div> <br class="spacer" /> <div class="footer"> </div> </div> </body> </html>