What is base rate neglect?
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The Bias: A test is 99% accurate for a rare disease. Why might a positive result still likely be wrong?
Because the disease is so rare, false positives can outnumber true ones. Ignoring how common something is overall leads to wrong conclusions. Source: Wikipedia – Base rate fallacy
Where It Shows Up: Where does it show up?
Medical screening and security alerts. Rare targets plus imperfect tests mean many false alarms. Source: Wikipedia – Base rate fallacy
The Fix: Fix?
Start with how common it is, then adjust for the evidence. Begin with base rates. Source: Wikipedia – Base rate fallacy