From engineering design practice, where the notion is traced to Bernard Forest de Bélidor (La science des ingénieurs, 1729).
Sizes capacity as a multiple of the expected load, with the multiple set by how bad a failure would be and how uncertain the estimates are.
When to reach for it
When designing anything that must not fail, such as a system's capacity, a cash reserve, or a supply buffer, and the load estimates carry real uncertainty.
How it runs
- Estimate the expected load from the best data.
- Estimate its realistic upper range.
- Weigh the consequences of failure.
- Judge how uncertain the load model is.
- Choose a factor to match, using industry norms where they exist.
- Set capacity at load times the factor, and record why.
Where it sits in SOLVE eX
Go to the source
- La science des ingénieurs dans la conduite des travaux de fortification et d'architecture civile, the attribution is Isaac Elishakoff's, 1729