Do you know a few "rules of thumb" used in statistical or computer science? Or in business analytics?

Do you know a few "rules of thumb" used in statistical or computer science? Or in business analytics?



Pareto rule:
- 80% of the effects come from 20% of the causes
- 80% of the sales come from 20% of the customers

Computer science: "simple and inexpensive beats complicated and expensive" - Rod Elder

Finance, rule of 72:
- Estimate the time needed for a money investment to double
- 100$ at a rate of 9%: 72/9=8 years

Rule of three (Economics):
- There are always three major competitors in a free market within one industry

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