In desperation I asked Fermi whether he was not impressed by the agreement between our calculated numbers and his measured numbers. He replied, 'How many arbitrary parameters did you use for your calculations?' I thought for a moment about our cut-off procedures and said, 'Four.' He said, 'I remember my friend Johnny von Neumann used to say, with four parameters I can fit an elephant, and with five I can make him wiggle his trunk.' With that, the conversation was over.
About this quote
- What does it mean?
- Fermi critiques the use of too many adjustable parameters in a scientific model, suggesting it can fit any data without proving validity.
- In plain terms
- Using too many free numbers in a calculation makes it easy to match results but doesn't prove the theory is right.
- What can you take from it?
- Scientific models should be simple and predictive, not just flexible enough to fit existing data.
Where it applies
Putting it to work
Questions to consider
- How many parameters are too many?
- Can a model fit data but be wrong?
Another view
Some complex systems inherently require many parameters to be accurate.
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