Explanations of Baseball Statistics

I realize that some of the statistics and categories I use in my analysis of the HOF ballot may be unfamiliar, so below is a brief rundown of the less-obvious items, plus a couple of notes. I have not bothered with any basic stats like RBIs or Slugging Percentage, nor with things that should be easy to interpret, such as SO/BB or catcher's ERA. Unless otherwise noted, all stats come from Baseball-Reference.com.

+ For any stat that ends with a plus sign, 100 is defined as MLB average, and higher is better.
Best year An asterisk indicates that the player led the league in a particular category that year.
dWAR Defensive Wins Above Replacement. This compares a player's defensive strength to those of other players at the same position. Baseball-Reference currently displays dWAR with an additional adjustment, attempting to relate a player's defense to some universal standard, which I think is ridiculous. This also results in the positional adjustment being counted twice. The version I display is an older, more basic representation, such that WAR = oWAR + dWAR.
ERA+ Earned-Run Average +. This compares a pitcher's ERA to those of other pitchers during the same seasons, adjusted for home ballpark, thus resulting in a neutralized figure.
escaping jams Specifically, this refers to the pitcher preventing a runner from scoring, when the runner reached third base with less than two outs.
n Statistics which are preceded by an "n" are my own original stats, marked as such to distinguish them from more official statistics.
nBIP Nathan's bases per inning pitched. This original stat is an upgraded version of WHIP, taking into account several additional batting and baserunning events. Included are hits, extra-base hits, reach on error, unintentional walks, hit by pitch, sacrifice flies, ground into double plays, stolen bases, caught stealing, pickoffs, wild pitches, passed balls, and balks. For comparison, the 2013 major league average, when 4.17 runs were scored per game, was 1.636, versus a WHIP of 1.300. In 2000 (5.14 runs per game), the MLB nBIP was 1.850, with a WHIP of 1.468.
nFB/9 Nathan's Free Bases per Nine Innings. This original stat shows how many additional bases a pitcher "gave" to the hitters. Below 2.0 is excellent; above 4.0 is terrible. Note that this statistic has since been subsumed by nBIP.
FB = (BB - IBB) + HBP + (1.5 * WP) + (1.5 * Bk) - GDP - PkO.
nHIT+ Nathan's Hitting +. This was originally based on OPS+, but with greater weight to OBP. Now it has been changed to a more comprehensive statistic, giving proper weight to various elements. (It is very similar in nature to Fangraphs' wRC+.)
nPIT+ Nathan's Pitching +. Another original statistic, this one very similar to ERA+. However, instead of being based on the pitcher's ERA and league ERA, it is based on run average (listed on Baseball-Reference as RA9) and a wonderful stat called RA9avg. Thus, it adjusts not only for ballpark and era, but also for the pitcher's role (starter or reliever) and for the team's fielding strength. This is a much more intelligent approach to compensating for defense than the ridiculous FIP (Fielding-Independent Pitching), which pretends that pitching is nothing but walks, strikeouts, and home runs.
nR/G Nathan's Runs per Game. This original stat attempts to determine how many runs a lineup consisting of nine of this player would score in a completely average offensive environment. Major League average is defined as 4.42.
OPS+ On-base Plus Slugging +. This compares a hitter's on-base percentage and slugging percentage to those of other hitters during the same seasons, adjusted for home ballpark, thus resulting in a neutralized figure.
oWAR Offensive Wins Above Replacement. This compares a player's offensive production to other players at the same position, rather than holding shortstops and left fielders to the same offensive standards.
Rtot/yr Total Fielding Runs per Year. This measures how many runs above or below average a fielder was versus others at the same position, prorated based on 1,200 innings. Although Baseball-Reference rounds their numbers to the nearest integer, I expand it to the nearest tenth.
Note that this stat is based on Total Zone Rating, rather than more accurate methods like Ultimate Zone Rating. There is a superior stat available, Rdrs/yr (Defensive Runs Saved per year), but it does not exist for seasons prior to 2002, by which point most of the players currently on the ballot were already past their primes. Not until the 2017 ballot will we even begin seeing players with ten years' Rdrs available, so I won't be using it for my write-ups for a while yet.
WAA Wins Above Average. This is very similar to WAR, but uses a dead-average major leaguer as its base. For a single season, it doesn't generally matter whether you use WAR or WAA, but for a career, the results can be very different. WAR tends to favor players who played respectably, but perhaps not exceptionally, for a long period of time; WAA favors players who maintained a high level of play, but may not have stuck around all that long. You can think of it as WAR reflecting the player's overall accomplishments, with WAA showing how "good" he was.
WAR Wins Above Replacement. This is the most comprehensive player-analysis tool available, though it is far from perfect. Unlike most of the figures I list, WAR is not a true statistic, but rather an abstraction, which attempts to combine all of a player's regular-season performance into a single number. That number takes the form of: How many more wins was this player, by himself, worth to his team versus a hypothetical minor leaguer in the same situations? The figure includes a positional adjustment, so that players are compared to people at the same position.
WAR is broken down into three components: offensive (oWAR), defensive (dWAR), and pitching (pWAR). Currently, I do not list oWAR or dWAR for pitchers; only pWAR. This is because oWAR tends to be a very small number, and dWAR seems to be deeply flawed for pitchers.
WHIP Walks plus Hits per Inning Pitched. Roughly, how many baserunners the pitcher allowed per inning.

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All writings are copyright 2013-2014 by Nathan Robson and may not be reproduced without the express written consent of the copyright owner. All rights reserved. Latest book in a series: Ventriloquism for Dummies.