The base-rate surprise
See how rare events change what a positive detector result means.
THE EXPERIMENTReady when you are
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How it works
How it works.
P(event | positive) = sensitivity × prevalence / [sensitivity × prevalence + (1 − specificity) × (1 − prevalence)].
Assumptions and limits
An abstract detector with independent cases and fixed rates; not a medical interpretation tool.