ABSTRACT
This chapter defines what we mean by Factors, Rates and Ratios, and how we might use these to create estimates by analogy. In estimating we frequently talk about 'Metrics'. The term 'Metric' in a business sense is a statistic that measures an output of a process or a relationship between a variable and another variable or some reference point. An Estimating Metric is a value or statistic that expresses a numerical relationship between a value for which an estimate is required, and a Primary or Secondary Driver (or parameter) of that value, or in relation to some fixed reference point. Rate Metrics are expressions of how something changes in relation to some measurable Driver, attribute or parameter, and would be expressed in the form of a [Value] of one attribute per [Unit] of another attribute. Caveat augur is important to know which way round a driver works in relation to the estimate and the other drivers.
