From Francis Galton's report on guessing an ox's weight (Vox Populi, 1907), developed by James Surowiecki (The Wisdom of Crowds, 2004) and Scott E. Page (The Difference, 2007).
Collects independent estimates from a varied group and takes the median, which often beats any single expert's guess because individual errors cancel out.
When to reach for it
When a number has to be estimated, such as a cost, a duration, a market size, or a probability, and several informed people can give independent guesses cheaply.
How it runs
- Pose a precise question with a numeric answer.
- Recruit a varied pool of informed people, ideally fifteen or more.
- Collect estimates privately, before any discussion.
- Take the median and report the spread.
- Investigate a wide spread before relying on the median.
- Score the crowd against the outcome, and refresh the pool.
Where it sits in SOLVE eX
Go to the source
- Vox Populi, Nature 75, 1907
- The Wisdom of Crowds, 2004
- The Difference, 2007