Wideband Delphi

Delphi Estimation is an effort estimation technique based on reaching consensus. It was first developed at the RANK Corporation in the 1940s. The Wideband version of Delphi Estimation was developed in the 1970s, and is called Wideband because it involves much more discussion and communication between those creating the estimates.

Wideband Delphi Estimation is performed during a meeting, and involves two roles:

  • Coordinator: This is the person who will run the meeting (as project manager this could be you or your could get someone else to perform this role).
  • Experts: These are the specialists who will create the estimates. In my experience it’s better to invite a few too many Experts to the meeting rather than too few.

The steps of Wideband Delphi Estimation are as follows:

  1. The Coordinator gives the Experts a Specification Form and an Estimation Form. The Specification Form should contain space for the Expert to create a Work Breakdown Structure. The Estimation Form allows the Experts space to provide estimates against all elements in the WBS, and any assumptions made.
  2. A discussion is held between everyone involved where all issues related to estimation are discussed.
  3. Experts fill out both forms anonymously.
  4. The Coordinator collates and distributes a summary of all estimates (this can be done in the meeting or afterwards)
  5. A follow-up meeting is called for the Experts to discuss any items which stand out, or where estimates differ by a significant amount between Experts.
  6. Experts fill out the forms again. The process is then repeated from step 4 until all major issues are resolved.

Advantages of Wideband Delphi

  • It uses an iterative approach to reach a consensus on estimates.
  • By completing forms anonymously those unwilling to speak up during the group discussion for whatever reason, are still able to contribute their opinions.
  • In the process of conducting the estimation, all participants become better educated about all aspects of the project.

Disadvantages of Wideband Delphi

  • What happens when the Experts fail to reach a consensus or refuse to reach a consensus?
  • The Experts may be subjectively biased, for example, if they all want to achieve the same goal, or if they come from the same business unit etc. This could result in dramatically underestimating effort or missing large sections from the WBS.


Wideband Delphi Estimation is a simple way of creating estimates based on consensus. It extends Delphi Estimation by adding the group communication stage and iterative loop. This article should give you enough information to try it when managing your next project or program – just remember to keep a mental note of the pitfalls.