Definition
Plain language
Just repeating how often something happens on average instead of predicting the specific case.
As stated in the literature
A constant forecast equal to the marginal outcome frequency; here the 0.50 prediction that yields a Brier score of 0.250 on a balanced set.
Also called: base rate answer
Why it matters: It sets the floor any real forecaster must beat, since a system that only echoes average frequencies looks calibrated on paper while providing no information about the specific case in front of it.
For example, saying "there's a 50% chance" to every coin-flip-like question gives you a respectable-looking score without ever distinguishing the likely cases from the unlikely ones.
Heard on the show
“They’re worse than the base-rate answer.”Episode 251 — When a Fake Dashboard Makes an AI Agent Just as Confident