Ignoring statistical base rates (how common something is in the population) in favor of specific case information or stereotypes.
A doctor sees symptoms matching a rare disease and diagnoses it, ignoring that the base rate (how common the disease is) makes a common disease with similar symptoms far more likely.
Individual case information is more diagnostic than population statistics—base rates are often more informative than case-specific details.
Thinking, Fast and Slow
Daniel Kahneman
Judging the frequency or probability of events by how easily examples come to mind, leading to overestimation of vivid, recent, or emotional events.
Judging probability by similarity to stereotypes or prototypes, while ignoring base rates and sample size.
Judging probability by similarity to stereotypes or prototypes, while ignoring base rates and sample size.
Fast, automatic, unconscious cognitive processing that operates through pattern recognition and associative memory without deliberate effort.
Judging a conjunction of two events (A and B) as more probable than one of the events alone (A), violating basic probability rules.
Why do people judge 'librarian' as more likely than 'farmer' for someone who is shy and likes poetry, even though farmers vastly outnumber librarians?
A doctor sees symptoms that match a rare disease affecting 1 in 10,000 people. The symptoms also match a common condition affecting 1 in 100 people. What error might base rate neglect cause?