Concepts
Health psychology/Cognitive biases · Clinical reasoning
Base-rate neglect
What it means
Ignoring the underlying prevalence of a condition when estimating its probability in a given patient.
Worked example
Chasing a rare zebra in a low-prevalence setting while ignoring the common cause.
In the exam
Faced with a common presentation, a clinician pursues an exotic rare diagnosis, disregarding how vanishingly uncommon it is in this population.
What settles it
Base-rate neglect ignores PREVALENCE. Representativeness is the broader error of judging by prototype-fit, which often causes base-rate neglect.
Classically confused with
Representativeness
Source: Tversky & Kahneman