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Wideband Delphi Estimation

The Wideband Delphi estimation method was developed in the 1940s at the Rand Corpora-
tion as a forecasting tool. It has since been adapted across many industries to estimate
many kinds of tasks, ranging from statistical data collection results to sales and marketing
forecasts. It has proven to be a very effective estimation tool, and it lends itself well to soft-
ware projects. *
The Wideband Delphi estimation process is especially useful to a project manager because it
produces several important elements of the project plan. The most important product is the
set of estimates upon which the project schedule is built. In addition, the project team cre-
ates a work breakdown structure (WBS), which is a critical element of the plan. The team
also generates a list of assumptions, which can be added to the vision and scope document.

The discussion among the team during both the kickoff meeting and the estimation ses-
sion is another important product of the Delphi process. This discussion typically uncovers
many important (but previously unrecognized) project priorities, assumptions, and tasks.
The team is much more familiar with the work they are about to undertake after they
complete the Wideband Delphi process.
Wideband Delphi works because it requires the entire team to correct one another in a
way that helps avoid errors and poor estimation. While software estimation is certainly a
skill that improves with experience, the most common problem with estimates is simply
that the person making the estimate does not fully understand what it is that he is esti-
mating. He may be an experienced software engineer, but if he has not fully explored all
of the assumptions behind the estimate, the estimate will be incorrect. Delphi addresses
this problem through the discussion of assumptions and the generation of consensus
among the estimation team members.

NOTE
The Wideband Delphi process described here depends on a vision and
scope document. It is possible to estimate a project without a vision and
scope document, instead relying solely on the project team’s under-
standing of the organization’s needs. However, if there is no vision and

scope document for the project, most project managers will find that
writing one will improve the project far more than trying to estimate
without it. (Chapter 2 describes how to develop a vision and scope doc-
ument as part of the software project planning activities.)

* The repeatable process for Wideband Delphi was developed in the 1990s by Mary Sakry and Neil
Potter of The Process Group. Potter and Sakry offer a software estimation workshop based on their
process. Information on their training products can be found at http://www.processgroup.com.

ESTIMATION 39