Thinking books · Decision making · Kahneman, Sibony & Sunstein, 2021

Noise — the big ideas

On unwanted variability in judgement — the same case judged differently by different people, or by the same person twice.

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The big ideas

Noise is distinct from bias: bias is a consistent offset, noise is scatter. Organisations measure the first and are usually unaware of the second, which is often larger.

A noise audit — having several people judge the same cases independently — reliably shows far more disagreement than anyone expects, including among experts.

Occasion noise: the same judge decides differently depending on the hour, the weather or the previous case.

Decision hygiene reduces it: break a judgement into independent components, judge each separately, use a shared scale, and aggregate — rather than forming a holistic impression.

Practise it — no need to have read it

Take a judgement your team makes regularly. Have two people assess the same case independently and compare.

A hint: The gap is usually the surprise. Nobody thinks they are the noisy one.

Where it shows up in real life

• Hiring decisions
• Performance review
• Any repeated assessment

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