Efficiency statistics: what each ratio rewards
Team-sport statistics are ratios designed to answer specific questions, and each choice of numerator and denominator is a judgment about what counts.
Basketball shooting efficiency. Field-goal percentage treats a two-pointer and a three-pointer as equal makes, which flatters inside scorers. True shooting percentage corrects this by valuing attempts in points-equivalent terms: TS% = PTS ÷ (2 × (FGA + 0.44 × FTA)). The 0.44 factor approximates free-throw trips per attempt (two free throws occur on many, not all, foul possessions). A player with 24 points on 10/20 shooting and 4/5 free throws has TS% = 24 ÷ (2 × (20 + 0.44×5)) ≈ 54% — right around the 54-56% band typical of league-average efficiency, and the honest comparison across roles.
Football passing. Completion percentage rewards accuracy but ignores distance; a 5-yard checkdown and a 40-yard strike count the same. Passer rating combines completion rate, yards per attempt, touchdown rate and interception rate into a bounded index; yards per attempt is the crude-but-persistent correlate of scoring. Any Agility T-Test on passing needs both: one for precision, one for aggression.
Baseball. Batting average (hits ÷ at-bats) ignores walks and power; on-base percentage (reaching by hit or walk, over plate appearances) fixes the first; OPS (OBP + slugging) sums them into one number that correlates well with run production despite its simplicity. WHIP (walks plus hits per inning pitched) is the pitcher's mirror: a rate statistic with a familiar scale where roughly 1.00 is excellent.
Soccer possession and passing stats are the cautionary set: possession % describes territory control, not threat — a team can dominate the ball and lose. Read every percentage next to a *conversion* measure (shots on target, expected goals) before drawing conclusions.
So before reading any team-sport percentage, ask the four questions the formula was built around:
- What does the numerator count? Points, hits, or completions — and are all of them equally valuable?
- What is in the denominator? Attempts, innings, or possessions — and does it adjust for opportunities?
- What is deliberately excluded? Walks in batting average, distance in completion percentage, playmaking in TS%.
- What number completes the picture? Pair the efficiency stat with one volume or creation measure.