In the mathematics of physics, there are two essential types of values in all calculations - Scalars and Vectors.
Scalars are isolated values, with no outside context. Indeed They remain the same regardless of any context. A common example would be mass. An object has a mass of 1 Kilogram no matter where it is, or how much physical space it occupies. The context of the object cannot change the scalar value of its mass.
- The number of stories produced in the last iteration.
- The number of database rows selected on average for a transaction.
- The number of defects found in thise release to production.
Vectors are contexted values, and can change depending on that context. An object has weight, dependent on both the mass value and gravity context of the object. An object with high mass, may still have no weight in the corresponding context of gravity.
- The change in the productivity of value as a function of time and cost as the project moves through its maturation process.
- The estimated productivity needed to complete the project on or before a need date, at or below the planned budget to achieve the needed Return on Investment on the need date, so the break even date can be announced to those paying for our work.
But most specifically, vector values allow the calculations of change over time. Numbers (scalars) without context (vectors) are not metrics.
It is meaningless to say that cost to operate the IT Service Desk has doubled within the last ten years, without also showing how the number of employees has tripled in the same time.
It is meaningless to say a self-selected 120 projects exceeded their estimated cost and duration without an assessment of the credibility of that original estimate and the determination of the Root Cause of that overage.
It is meaningless to say the end date and cost can be forecast with saying something about the underlying uncertainties in effort size, risk, inter-dependencies, changing requirements, defect rates, labor absorption rates, integration issues, performance issues, and complexities of emerging behaviours once the system starts to come together and applied to fulfill the needed capabilities.
When we hear about small sample sized forecasts of same sized work activities, or selecting the next priority item to work on without considering the inter-dependencies of past work items or future work items - we're speaking about Scalar numbers, not Vector numbers.
Vectors state magnitude and direction. Open Loop control only states magnitude. Use it at your own risk.
