Chapter 8: Calibration and Historical Data

Overview

Applicability of Techniques in This Chapter
	Calibration with Industry-Average Data	Calibration with Organizational Data	Calibration with Project-Specific Data
What's estimated	Size, Effort, Schedule, Features	Size, Effort, Schedule, Features	Size, Effort, Schedule, Features
Size of project	S M L	S M L	S M L
Development stage	Early-Middle	Early-Middle	Middle-Late
Iterative or sequential	Both	Both	Both
Accuracy possible	Low-Medium	Medium-High	High

Calibration is used to convert counts to estimates—lines of code to effort, user stories to calendar time, requirements to number of test cases, and so on. Estimates always involve some sort of calibration, whether explicit or implicit. Calibration using various kinds of data makes up the second piece of the "count, then compute" approach described in Chapter 7, "Count, Compute, Judge."

Your estimates can be calibrated using any of three kinds of data:

• Industry data, which refers to data from other organizations that develop the same basic kind of software as the software that's being estimated

• Historical data, which in this book refers to data from the organization that will conduct the project being estimated

• Project data, which refers to data generated earlier in the same project that's being estimated

Historical data and project data are both tremendously useful and can support creation of highly accurate estimates. Industry data is a temporary backup that can be useful when you don't have historical data or project data.