Estimation is crucial element of software project planning. Hundreds of documented software estimation methodologies, tools, and models exist. Some of the earliest ones estimated the software cost as a percentage of the hardware cost. For most, the output is an estimation of staff effort from a wide variety of inputs. many of the methods use an analytical formula based on cost drivers, which typically are project characteristics such as system size, system domain, complexity, and development methodology. The tools and methodologies are primarily based on data from past projects
['Linda Laird']
The Limitations of Estimation