When a vivid case drives certainty, ask for the base rate…
When a vivid individual case makes you feel certain about probability, explicitly ask 'what is the actual frequency of this event in the relevant population?' before forming any judgment.
When This Fires
- A dramatic example is shaping your risk assessment (startup success, medical risk, system failure)
- You feel very certain about a probability based on one or two memorable cases
- Someone is persuading you with a compelling anecdote rather than data
- You're about to make a decision and your confidence comes from a story, not statistics
Common Failure Mode
Acknowledging the base rate but letting the vivid case override it anyway. "I know most startups fail, but this one is different." The base rate becomes a disclaimer rather than an anchor. Your judgment still comes from the vivid case — you've just added a caveat to feel rational about an irrational estimate.
The Protocol
When a vivid case triggers certainty: (1) Name the case explicitly: "I feel certain because of [specific example]." (2) Ask: "What is the actual frequency of this outcome in the relevant population?" (3) Look up or estimate the base rate. (4) Start your judgment from the base rate, then adjust for case-specific factors — not the other way around. The base rate is the anchor; the vivid case is the adjustment.