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MIXORA CONCEPT

Base-rate neglect

Giving too little weight to how common an outcome is before considering case-specific evidence.

thoughtStrong evidence
IN PLAIN LANGUAGE

A vivid test result or detailed description can dominate judgment even when the underlying event is rare. Good reasoning combines the prior frequency with how diagnostic the new evidence is.

What “Strong evidence” means

The core definition or effect is well established across authoritative standards, foundational research or a broad research literature. The label does not make every practical prediction certain.

Marker-board illustration created specifically to explain Base-rate neglect: Giving too little weight to how common an outcome is before considering case-specific evidence.VISUAL EXPLANATION · MARKER BOARD
Giving too little weight to how common an outcome is before considering case-specific evidence.
EXAMPLE

A rare paint defect should not become the default diagnosis merely because its symptoms sound memorable.

COMMON CONFUSION

Using a base rate does not mean ignoring individual evidence; it supplies the starting point that evidence updates.

ASK YOURSELF

What proportion of comparable cases had this outcome before seeing the new clue?

RELATED CONCEPTS
thoughtProbability

A formal way to represent uncertainty or long-run regularity, depending on the interpretation used.

thought × bridgeRepresentativeness heuristic

Judging probability by resemblance to a familiar category or story, sometimes with too little attention to base rates.

thoughtAvailability heuristic

Judging frequency or likelihood partly by how easily examples come to mind.

thought × bridgeEvidence

Information that raises, lowers or otherwise constrains rational confidence in a claim.

References

Last reviewed

  1. 01
    Judgment under Uncertainty: Heuristics and Biases

    Amos Tversky & Daniel Kahneman · 1974 · Science

    Classic account of representativeness, availability and anchoring in judgment under uncertainty.
    Academic source
What the source labels mean
Primary source
Original work, experiment, standard or historical text.
Academic source
Scholarly research or review published for an academic audience.
Reference source
An expert standard, encyclopedia or institutional explanation that summarizes a field.
General reference
A practical specialist resource useful for application, but not treated as decisive research by itself.