Reading the Numbers
Base Rates: The Number You Forgot to Ask For
5 min read
TL;DR
Before asking whether something is impressive, ask how often it happens anyway. Most sports claims that sound remarkable are describing an ordinary base rate in dramatic language.
The question that deflates most stats
"He has hit safely in eight of his last ten." Sounds like form. But a .300 hitter with four at-bats a night gets a hit in about 76% of his games by default. Eight in ten is 80%. That is a normal week, described as a streak.
The base rate is the answer to *how often does this happen when nothing special is going on?* Without it, every number sounds meaningful, because you have nothing to compare it to.
Where the effect is strongest
Base rates matter most when the event is common but feels rare:
- A 60% free-throw shooter misses two in a row 16% of the time — about one trip in six.
- A .300 hitter has a hitless four-at-bat game 24% of the time.
- Any given NBA starter will have a game 40% above his scoring average several times a season, purely from variance.
None of these require a story. They are what the distribution does on its own.
Building the habit
When you meet a sports statistic, ask three things in order:
- How often does this happen normally? That's the base rate.
- How many chances were there? Ten games is a different claim than ten seasons.
- Was this picked out after the fact? If someone searched for the streak, finding one is not surprising.
That third question is the subject of its own lesson — see Hot Streaks and Survivorship.
Keep these
- Always ask how often the thing happens anyway
- A 60% free-throw shooter misses two straight 16% of the time
- Common events described dramatically are the most frequent trap
Up next
Correlation, Causation, and Sports Narratives