We use defined processes whenever possible because with them we can crank up unattended production to such a quantity that the output can be priced as a commodity. In the long run, making successful products using (more costly) empirical process control turns out to be much cheaper than reworking unsuccessful products using defined process control.
Ken Schwaber, Agile Project Management with Scrum
| Defined Process Control Model | Empirical Process Control Model |
| ♠ well-defined set of inputs | ♥ imperfectly defined inputs |
| ♦ each step of work is completely understood | ♣ frequent inspection and adaptation |
| ♣ the same outputs are generated every time | ♠ unpredictable results |