One of the criteria for a good MOE (not a requirement) is that the MOE is substantially independently valued as an outcome. The incidence of highly coupled MOEs is not frequent. When it does occur, it is inevitably for one of two reasons:
- the two MOEs that are coupled in value are contributors to the real MOE. An example would be Reliability and Maintainability, where the real concern is Availability, e.g. with a bank and an ATM
- there is double-counting in the MOEs, e.g. Life Cycle Cost and Development Cost.
The usual number of MOEs necessary to capture most of the tradeable value beyond requirements (at least 95% of the actual trade space, desirably closer to 98%) is few, typically from 5 to 15 or so.