Why Size As Part of Estimation?

In this blog post, Thomas Cagley discusses the need to size the scope of a software development project during the estimation activity. His opinion is that the main benefit of sizing is the conversation that this effort generates. But as managers and estimators are numbers people, it is not safe to start with a topic as touchy as talking.

Size is traditionally a important cost indicator in engineering projects. Software estimation based on size can be expressed as a function of size, complexity and capabilities: E = f(size, complexity, capabilities). Function points and user stories are measures that can be used to size software development projects. Estimating size provides a lot of benefits like a better understanding of requirements and risks. Sizing the software allows also to discuss velocity or productivity as a separate entity. Isolating the size of the work allow also to modify estimates more easily when something change in the scope, resources or schedule. Even if estimates are wrong by definition, the conversation that estimation generates are very valuable for software development projects.