Software Estimation: Demystifying the Black Art

Chapter 15. Use of Multiple Approaches

Applicability of Techniques in This Chapter

	Use of Multiple Estimation Approaches
What’s estimated	Size, Effort, Schedule, Features
Size of project	S M L
Development stage	Early–Late
Iterative or sequential	Both
Accuracy possible	High

No single estimation technique is perfect, so using multiple approaches is useful in many contexts. The most sophisticated commercial software producers tend to use at least three different estimating approaches and then look for convergence or spread among their estimates. Convergence among the estimates tells you that you probably have a good estimate. Spread tells you that there are probably factors you have overlooked and need to understand better. This technique applies equally ...