Base Rate Fallacy

The tendency to ignore general statistical information (base rates) in favor of specific, individual information.

Specific, vivid details are more emotionally compelling than abstract statistics. Stories about individuals override our ability to reason about probabilities.

• Fearing terrorism more than heart disease despite heart disease being far more common.
• Believing a positive medical test means you definitely have the disease, ignoring the low prevalence rate.
• Assuming someone described as 'quiet and organized' is a librarian rather than a salesperson, ignoring that salespeople vastly outnumber librarians.

• Always consider the base rate before evaluating specific evidence.
• Ask: 'How common is this in the general population?'
• Use Bayesian thinking: update your beliefs based on both prior probability and new evidence.
• Be wary of dramatic stories that override statistical reasoning.