Software Estimation: Demystifying the Black Art (Best Practices (Microsoft))

17.1 Usual Elements of a Standardized Procedure

Based on the typical estimation flow described in Chapter 16, "Flow of Software Estimates on a Well-Estimated Project," a standardized estimation procedure typically does the following:

• Emphasizes counting and computing when possible, rather than using judgment

• Calls for use of multiple estimation approaches and comparison of results

• Communicates a plan to reestimate at predefined points in the project

• Defines how the required estimation approach changes over the course of a project

• Contains a clear description of an estimate's inaccuracy

• Defines when an estimate can be used as the basis for a project budget

• Defines when an estimate can be used as the basis for internal and external commitments

• Calls for archiving estimation data and reviewing effectiveness of the procedure

For the standardized estimation procedure to do its job, it's important that the organization treat the procedure as a standard. Deviations from the procedure need to be justified in writing, and they should be rare.

The procedure itself should be documented in a "Software Engineering Standards" document or a "Standardized Estimation Procedure" document. The procedure itself is then subject to formal change control. The procedure can be changed at the end of a project, motivated by a desire to improve the procedure's accuracy for future projects. The procedure should not be changed "in flight." Such changes are too prone to bias that will undermine both the accuracy of the specific estimate in question and the effectiveness of the procedure for future projects.