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What Factors Affect HR-FB Rate-
08-09-2017, 12:53 PM
Post: #1
What Factors Affect HR-FB Rate-
In the past few weeks, homer per fly ball rate is a hot topic at FanGraphs and round the baseball blogosphere. Dave Cameron sparked a lively discu sion with this post about Matt Cain, after which showed that Giants pitching coach Dave Righetti has been able to get much better than average HR/FB rates out of a number of his starters. Another interesting article suggests that HR/FB rate may have something to do with pitch movement. At this time, it appears clear that HR/FB rate might not be completely luck. It might have a lot of luck involved, but there are several factors that may decrease or increase this statistic. Using the vast FanGraphs database and some regre sion modeling, we are able to search for these 4 elements Nike Lebron and discover simply how much they matter. The data examined is from 2002 to 2009, leaving last season out of the data set in to test the models forecasting ability later. This information is for starting pitchers only, and only people who threw 80 or even more innings. Also, pitchers who changed teams throughout the season were excluded. There were numerous independent variables tested, and countle s models examined. For brevity, I wont take you through ever iteration from the proce s, but instead tackle categories of variables. Park Factor This is the variable that is probably the most obvious to incorporate. Many studies have shown that a players HR/FB rate depends on his home park, which analysis concurs. The variables coefficient is positive and significant in the 99-percent level, meaning there is just one 1-percent chance the relationship between this variable and the dependent variable (HR/FB) is completely random. The only surprise here is the coefficient for park factor has a relatively low elasticity, which means it does not po se s a large impact on HR/FB rate. This is probably due to the fact that park factor only controls for about 1 / 2 of the games a pitcher starts. This variable could be improved by making it a weighted average of all of the parks the pitcher played in over the course of the season, but that's way too time intensive with this end. Pitcher Skill Using xFIP as an independent yields a significant coefficient, but that is too vague of the answer. Just what about xFIP matters for HR/FB rate? It works out that both K/9 and BB/9 yield significant coefficients at the 99-percent level. The former includes a negative coefficient and the latter includes a positive, and therefore more strikeouts and fewer walks led to a lower HR/FB. For K/9, this shows that pitchers who mi s bats regularly may be able to suppre s their HR/FB rates. Nike LunarEpic Low Flyknit This is not very surprising if hitters cannot put the ball in play against a pitcher, they may be le s inclined to square up a pitch and drive it when they make contact. For BB/9, the interpretation is a little le s obvious. The idea put forth here is that walk rate measures a pitchers control. A pitcher with good control is le s likely throw balls out of the strike zone, thus the reduced walk rate, and also is le s likely to groove one on the middle. Plate Discipline For this section, FanGraphs variables for swing rates interior and exterior the zone, and phone rates in and out of the zone were tested, as well as first pitch strike percentage and swinging strike percentage. Of many of these variables, only one showed proof of rapport to HR/FB rate: O-Contact%. This variable had a significant negative coefficient, meaning that a lot more that hitters were getting in touch on pitches away from strike zone, the lower the HR/FB rate was for the pitcher. This tells us that balls hit away from strike zone are merely le s likely to be home runs. It doesn't mean they aren't apt to be hits, or perhaps extra base hits, but they're not leaving the park at the same rate as balls hit within the zone. This variable has a 99-percent significance along with a large elasticity, and therefore this variable highly effects the HR/FB rate. If a pitcher could consistently cause hitters to make contact with pitches outside the strike zone, they may be in a position to hold down their home run rate. Can pitchers continually bait hitters into swinging at pitches that they can hit, but not hit well? Thats an area for additional research. Batted Ball Percentages The four batted ball types were examined as independent variables: fly ball percentage, line drive percentage, ground ball percentage, and infield fly ball percentage. Nike Air Max 95 Women Of these four, the only variable which turned out to be have a significant effect on HR/FB is IFFB%. Including IFFB% yields an adverse coefficient which is significant in the 99-percent level. This will make a ton of sense. Infield flies po se s a zero po sibility of being home runs. Along with O-Contact%, these variables help remove batted balls which have little or no chance of leaving the sports event from the pitchers HR/FB percentage. What is more interesting here is that no other three batted ball variables po se s a significant coefficient. Although it has been shown that fly ball pitchers will often have better HR/FB rates than ground ball pitchers, the outcomes of the model suggest that it may convey more related to the rise in popups, rather than the capability to obtain a higher number of outs on fly balls towards the outfield. Pitch Velocity The variables tested revolved around the regularity and velocity of pitch types inside a hurlers arsenal. This category produced truly interesting results. From the pitch type variables, you make it towards the final model: average fastball velocity. The statistic FBv was proven to have a negative impact on HR/FB rate, significant at the 90-percent level. The better fastball a pitcher has, the better his HR/FB rate. At first this seems counterintuitive because fast pitches travel farther when hit. However, this result shows that HR/FB rate might have more details on being able to square up a pitch. High velocity pitches may simply be tougher to create solid contact with, allowing pitchers who Nike Air Max 90 throw harder to find a way with increased mistakes. Putting Everything Together After countle s regre sion models and variable combinations, the final model is thus: Elasticity is defined as the percent alternation in x for any percent alternation in y. With this use, you can interpret the K/9 elasticity as a 5 % increase in strikeout rate translating right into a one percent decrease in HR/FB rate. The r-squared for that model is 10-percent. Yes, this is a low r-squared. No, it does not invalidate the model. The significance of the independent variables are the most important thing here, and all of those values tend to be more than acceptable. The fact that the r-squared is just 10 % after fitting six significant independent variables implies that HR/FB is still very much impacted by randomne s or any other outside factors. This model gets us nearer to the heart of HR/FB rate, however it does not explain all of its variability, and perhaps nothing can. This does suggest that, while pitchers have some ability to impact their HR/FB rates, there are significant variables that they don't control, which explains the entire year to year fluctuations for pitchers who undergo no other noticeable changes. The next logical question is does the model work? Using this model to project 2010 HR/FB rates yields a smaller sum squared error and mean squared error than the usual naive estimator of 10.6 HR/FB rate. So, preliminarily, yes, it will. In the approaching days, this model is going to be accustomed to further the discu sion about HR/FB rate and look at if it is easy to continually outperform the mean.
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