Base Rate Fallacy
We ignore general statistical information in favor of specific case information.
The base rate fallacy (also base rate neglect or base rate bias) occurs when people ignore prior statistical information and focus on individuating information instead. When told that a taxi involved in a hit-and-run was blue, and that 85% of taxis are green, people overweight the eyewitness account and underweight the base rate. This leads to systematic errors in risk assessment and medical diagnosis.
What it looks like in the wild.
- Everyday life Disease Testing A patient tests positive for a rare disease affecting 1 in 10,000 people. Even with a 99% accurate test, most positives are false positives — but the patient panics, ignoring the low base rate.
Recognising a definition is not the same skill as spotting it.
Two scenarios from the app, with distractors drawn from the same family of biases — which is what makes them hard.
Someone avoids a certain neighborhood after hearing about one burglary, despite police data showing it's one of the safest in the city.
Lucas doesn't buy a popular book because his brother said it was boring, despite it being a bestseller with overwhelmingly positive reviews.
Biases rarely arrive alone.
Understand more. Assume less.
188 biases, 18,869 scenarios, and a record of how you actually decide.
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