Friday, August 8, 2008

TPC Reference Guide and Definitions

Last week my dad called to tell me that he had stopped by to check out the site, and though he liked what he saw, he didn't understand all the terms used in my posts. So, for the next 15 minutes we discussed things like BABIP, WHIP, GB%, and what they all mean. After our chat I realized that casual baseball fans like my dad might need a simple reference guide for terms and definitions. I'll try to list commonly used terms and definitions in this post, and if you all think of any I should add, let me know. If I can figure out a way to do it, I'll try and make this post a side bar link or something.

  • AB -- At-bat. Plate appearances minus walks.
  • BA -- Batting Average
  • BABIP -- Batting Average for Balls In Play. (Total Hits - Home runs) / (At-bats - Strikeouts - Home runs - Sacrifices). Shows how often a hitter reaches base after making contact during an at-bat. Generally, a BABIP of .300 is considered the norm, while a BABIP extremely above or below .300 indicates good or bad luck on the hitter's part.
  • BB -- Bases on Balls, or walks
  • ERA -- Earned Run Average. (Earned Runs) / (Innings Pitched / 9)
  • GB% -- Ground Ball Percentage. The percentage of all batted balls in play that result in a ground ball. Applies to pitchers and hitters.
  • FIP -- Fielding Independent Pitching. Essentially a modified ERA for pitchers. Eliminates the effect that defense has on ERA by only counting the stats that a pitcher has direct control over, i.e. walks, home runs, and strikeouts. FIP is usually considered a more accurate determination of a pitcher's ability than ERA. The formula for FIP is ((HR * 13 + (BB + HBP) * 3 - SO * 2) / IP) + League Factor (which is generally between 3.0 and 3.5 depending on the league and strength of competition). It should be noted that FIP does not compensate for a pitcher's fly ball to groundball ratio, which directly effects run production, and is usually considered a pitcher controlled ratio.
  • ISOP -- Isolate Power. (Slugging Percentage - Batting Average). Helps define a hitter's power isolated from his contact rates. Power hitters usually post an ISOP above .250.
  • LD% -- Line Drive Percentage. The percentage of all plate appearances that result in a line drive. Applies to hitters and pitchers.
  • OBP -- On Base Percentage. The percentage of a hitter's plate appearances that result in that hitter reaching base safely either through walks and hits.
  • OPS -- On Base Plus Slugging Percentage. Combines a hitter's ability to reach base with his power totals.
  • PA -- Plate Appearances.
  • SLG% -- Slugging Percentage. A hitter's total bases from hits divided by his total at-bats.
  • WHIP -- Walks or Hits per Innings Pitched. A statistic to help track how many batters a pitcher allows to reach base per inning.


Mike said...

Does BABIP include foul outs? So would someone who plays for the A's and has a huge amount of foul territory have a lower expected BABIP compared to someone who plays for the Yankees?

Adam G said...

I believe you are correct Mike. BABIP only leaves out walks, strike outs, and home runs. So foul balls would detract from a player's BABIP. However, foul ball outs would probably only account for a small percentage of a player's plate appearances, so I don't think there would be a huge dip in BABIP in a player from the Yankees began playing for the A's simply because of the increased foul territory.

Micah said...

You need to add FIP to this list. You use it a couple times in your recent pitching posts.

Adam G said...

You are correct sir! I'll add FIP later tonight.

I'll also try and do something about the micro charts in the top pitching prospects post.