A look at the data used in creating SIERA, Baseball Prospectus' new pitching metric.
Earlier this week we introduced the run estimator SIERA, providing a general summary of its purpose as well as the evolution of its development. Today, in Part 3, our focus will shift to the quantitative side of the metric, offering a detailed look at the data used to derive the formula as well as specifics pertaining to the regression analysis techniques used. The transparency should provide a better understanding of the integrity of such a process as well as a few insights into the SIERA-laden approach towards pitcher valuations.
Pitcher-on-pitcher violence explored again, for fun and profit.
Earlier this month we took a look at pitcher-on-pitcher violence, computing the rates at which hurlers fan their counterparts and seeing how the results compared to overall strikeout rates. Two stats were introduced: PW%, which divides pitcher whiffs by pitcher plate appearances, and PWO%, the rate of whiffing pitchers as a measure of the overall tally. The league averages from 1979-2008 for those with 20 or more pitcher plate appearances against, were 31.4 percent for PW% and 14.5 percent for PWO%, respectively. The hypothesis presented at the outset of that article was eventually confirmed in that, when compared to a control group, pitchers exceeding the league average PWO% in one year experienced a more substantial decline in K/9 in the subsequent season. Pitchers remaining in the same league from one year to the next experienced an aggregate decline of 0.05 of their K/9, with those making the AL to NL conversion gaining 0.25 whiffs per nine, and senior circuit tossers heading to the tougher league dropping 0.31 whiffs per nine.
Is there a surprise to be found in terms of the in-series pattern of home-field advantage?
In the first three articles of this series, we have studied what home-field advantage affects, who it affects most, and where it shows up most. We have found that home-field advantage affects nearly every aspect of a team's performance, including pitching, defense, baserunning, and offense. We found that the Rockies are the only team that has statistically significant home-field advantage, and that most other teams are bound to win about eight percent more games at home than on the road in the long-run. We also found that home-field advantage was larger in interleague games than intraleague games, larger in interdivision games than in intradivision games, and even within divisions, it was larger the further apart the teams played. This suggested that travel might be playing a significant effect in home-field advantage. Further evidence of this came from the fact that interleague games within teams in equivalent divisions (e.g. East vs. East) had smaller home-field advantages than interleague games where longer travel distances were involved.
Drilling down even more deeply into the subject to find out where, why, and how.
In trying to understand home-field advantage, we have asked what home-field advantage actually makes a team do better, and we have asked who has the biggest home-field advantage. The first article of this series answered the question of what home-field advantage actually makes you do better-everything, as home teams do better on walks, strikeouts, balls in play, and errors. They are better at pitching, hitting, baserunning, and defense, and all aspects of their games seem to improve. The second article of this series showed that most teams have pretty much the same size home-field advantage, with the exception of the Rockies. Even though natural luck can make a team look like they are particularly good or bad at home, the 29 non-Rockies teams are pretty much right around eight percent home-field advantage, plus or minus a little statistical noise.
An initial look at the extent of the home-field advantage in terms of its incidence on in-game results.
In every sport and at every level, the home team wins more games than the visiting team. While this is true in baseball, it's less the case than in other sports. Throughout baseball history, the home team has won approximately 54 percent of the games played. Nearly every aspect of the game has changed drastically over the last century, but home-field advantage has barely changed at all. Consider the home-field advantage in each decade since 1901:
To pitch well in save situations, or to not pitch well in non-save situations? That is not the question.
For the past several years, the perception that closers perform poorly in non-save situations has increased. These relief aces fail to look particularly sharp unless they're under pressure and have the game's fate in their hands. Our own experiences have helped fuel this idea; we've all been witness to an untouchable pitcher entering a game with a 3-0 deficit and allowing a few more runs to score while pitching an ineffective inning. Unfortunately, with the memory of these negative events in mind, a categorical bias emerges where every example only provides further evidence of closer ineptitude when the game is not on the line. Is this strictly a categorical bias, or are the results and discrepancies in data between save situations and non-save situations real and significant?
Potential first-rounder performances, and the updated Baseball Prospectus NCAA Top 25.
I must say, it seems strange to be writing about a college sport this week that isn't basketball. I mean, if I tell you that I like Arizona State and Clemson this weekend, how do you process that? I actually like the Sun Devils and Tigers in both sports, but on the maddest day of March, talking about the NCAA without mentioning Cinderella and sleepers seems... wrong. Still, I know enough to just send you over to Ken Pomeroy and John Gasaway at the other BP, and stick to what I know here.
What happens when pitching in a pinch? Do pitchers have something extra that they can put on the ball when they're in a jam?
"I think we just played the way we thought we should play. We swung it better, we had clutch hitting, we had clutch pitching. If you put all those things together you have a chance to win a few more games and be a little more exciting. That's what we are doing right now."
-White Sox manager Ozzie Guillen commenting after beating the Mariners 5-3 on August 10th
Will shares a few things he'll miss about Spring Training, but moves right into the injury news that affects the regular season, with updates on C.C. Sabathia, Jason Isringhausen, Mark Prior, Luis Ayala, and more.
You know what I'll miss about Spring Training? Day games. The way the schedule works out in the spring is great for me, as everything is wrapped up well before prime time. There's the downside of having to deal with the morning people, those sick people who think calling me at pre-caffeinated hours will do anything. But at this time every spring, people are packing up their stuff and heading home. There are more and more teams making a stop somewhere for exhibition games, but the trucks are headed back, and Opening Day is just days away. The "Turk" has finished most of his difficult work around the league while the reaperesque figure of Injury is just beginning his work. Teams spend these last days just before the season starts living in fear, just a bit, of injury coming to visit. Powered by Daring Fireball, on to the injuries: