ABSTRACT
The main reason for identifying both the Primary and Secondary Drivers is so that we can use them as an integral part of the estimating methodology and techniques we have elected to use. A Primary Schedule Driver would be one that we might use to indicate the overall duration or elapsed time for a project or product through to its completion, or to some major milestone. Secondary Drivers are those Drivers for the 'trivial many' in a Pareto sense. We have the simplest of all Estimating Relationships from which we can derive a simple Metric to get an 'Actual Value per Driver Unit'. Accuracy and precision are words that are frequently used interchangeably in some areas of society, but to estimators and other number jugglers, they do have distinctly different connotations. Compare this with Boehm's Cone of Uncertainty which is only a factor of four and is probably considered to be a Very Rough Order of Magnitude (VROM).
