What is Wide Band Delphi Estimation ?


Wide Band Delphi  (WBD) estimation approach is a technique that was developed in the 1940s at Rand Corporation. This approach involves a team of experts preparing individual estimates for a project, similar to the consensus-based approach for estimation. The Wide Band Delphi estimation approach is a more advanced version of the Delphi method, where the estimation team uses statistical methods to refine and improve the estimates.


The WBD estimation approach starts with the same steps as the consensus-based approach, where the project manager selects a team and a moderator, and the team consists of 3-7 team members with representation from all groups, such as development, testing, etc. The moderator should be familiar with the Delphi process, and it is ideal to have the project manager as part of the estimation team. However, the project manager should not be the moderator as he will have a stake in the outcome of the estimation.


Steps Involved in Wide Band Delphi Estimation


The first step is the planning phase, where the kickoff meeting takes place. During the kickoff meeting, the team explains the Delphi process, reviews the vision and scope document or any supporting documents as prerequisites, and discusses the goals of the estimation session. The team then brainstorm and notes down the assumptions, generates the initial work breakdown structure (WBS), and decides upon the unit for estimation.


The next step is individual estimation, where each estimator estimates the time required for each task, adds any additional tasks to the WBS, and includes any missing assumptions. The difference in the WBD approach is that each estimator also provides a range of estimates for each task, including an optimistic estimate, a pessimistic estimate, and a most likely estimate.


The third step is the estimation meeting, where the moderator shares the estimates so that estimators can see the range of estimates. The individual estimates are not shared, and the team members revise estimates based on group discussions. The estimates are revised until no estimator wants to change his/her estimates, and the estimators agree that the estimates are acceptable.


In the WBD approach, the moderator also uses statistical methods to refine and improve the estimates. The moderator calculates the average of the most likely estimates and determines the standard deviation of the estimates. The standard deviation is used to calculate the optimistic and pessimistic estimates. The moderator then asks the estimators to provide additional estimates based on the optimistic and pessimistic estimates.


Example of Wide Band Delphi Estimation Technique


An example of the WBD estimation approach is when there are three estimators, A, B, and C, who are told to prepare the time required to prepare test scenarios for a project. The initial estimations provided were A – 18 Hours, B – 38 Hours, and C – 58 Hours. The moderator then calculates the average estimate as 38 hours and returns this with their original estimates to the estimators.


Wide Band Delphi Estimation Technique


Figure: Iterations and Estimated Effort


The estimators then meet and discuss the estimates, and the initial estimations provided were A – 31 Hours, B – 32 Hours, and C – 33 Hours. The moderator then calculates the average estimate as 32 hours and asks the estimators if they agree with this as the estimate. The moderator also calculates the optimistic and pessimistic estimates based on the standard deviation of the estimates.


The final step is to assemble tasks and review results, where the project manager works with the team and collects the estimates from team members, compiles the final WBS, estimations, and assumptions, and reviews the final estimates with the estimation team. You can find additional details of the technique by reading this e-book From Guesswork to Accuracy: Mastering Software Test Estimation


Pros and Cons of  Wide Band Delphi :



  1. Consensus-Based Estimation: The Wideband Delphi Technique is a method for reaching a consensus when estimating effort.
  2. Effective Time Estimation: It is particularly helpful when estimating the time needed for a task.
  3. Involvement of Experienced Individuals: It involves experienced team members who provide individual estimates, enhancing the reliability of the results.
  4. Valid Estimates: The estimates come from the people who will actually perform the work, ensuring the validity of the estimates.
  5. Anonymity and Confidence: Anonymity is maintained throughout the process, allowing everyone to express their estimates confidently.
  6. Simplicity: It is a straightforward technique.
  7. Documentation of Assumptions: Assumptions are documented, discussed, and agreed upon, enhancing clarity.



  1. Need for Management Support: Successful implementation of this technique requires support from management.
  2. Possibility of Unfavorable Results: The estimation results may not always align with what management desires to hear.


The  Wide Band Delphi Estimation approach is an advanced version of the Delphi method, where the estimation team uses statistical methods to refine and improve the estimates. This technique is ideal for projects that require a more accurate and precise estimate. The WBD approach is similar to the consensus-based approach for estimation, where the team of experts prepares individual estimates, builds a complete task.

 Frequently Asked Questions (FAQ) on Wideband Delphi Estimation

1. What is the Wideband Delphi Estimation Technique?

The Wideband Delphi Technique is a structured and consensus-based estimation method used in project management and software development. It involves a group of experts providing individual estimates for a particular task or project, followed by a facilitated discussion to reach a consensus estimate.

 2. How does the Delphi Technique work?

Here’s a simplified breakdown of the process:
– A group of experts or team members is assembled.
– Each expert provides their independent estimates for the task or project.
– The estimates are collected and discussed.
– The group works together to reach a consensus estimate.
– This process may iterate until a consensus is achieved.

 3. What are the advantages of using the  Technique?

– Consensus-Based Estimation**: It encourages collaboration and consensus among experts.
– Involvement of Experienced Individuals**: Experts in the domain provide estimates, increasing the reliability of results.
– Valid Estimates**: Estimates come from those who will perform the work, ensuring validity.
– Anonymity**: Anonymity is maintained during estimation, allowing for honest input.
– Simple Technique**: It’s a straightforward and easy-to-understand method.
– Documentation of Assumptions**: Assumptions are documented and discussed.

 4. When should the Delphi Technique be used?

– It is useful for estimating project tasks, especially when multiple experts are involved.
– When there is uncertainty or lack of historical data for estimation.
– In situations where consensus among team members is crucial.

 5. Are there any disadvantages to using this technique?

– Management Support: Successful implementation may require support from management.
– Possibility of Unfavorable Results: The consensus estimate may not always align with management’s expectations.

 6. Can the Technique be used for all types of projects?

While it is versatile, the Wideband Delphi Technique is particularly beneficial for projects with:
– High uncertainty.
– Diverse teams with varying expertise.
– A need for consensus among team members.

 7. What role does the facilitator play in the  Technique?

The facilitator plays a crucial role in guiding the estimation process. They:
– Ensure the process is followed correctly.
– Manage discussions and conflicts.
– Help the group reach a consensus.
– May iterate the process if consensus is not initially achieved.

 8. How can I ensure the Technique is effective?

– Assemble a diverse group of experts.
– Clearly define the task or project to be estimated.
– Encourage open and honest communication.
– Follow a structured process with a skilled facilitator.
– Document assumptions and agreements.

9. Are there variations of the Wideband Delphi Estimation Technique?

Yes, variations exist, including:

– Modified Delphi: Involves feedback and re-estimation rounds.
– Wideband Delphi with Historical Data: Combines expert estimation with historical data analysis.
– Electronic Delphi: Conducted online, facilitating participation from geographically dispersed experts.

10. Can the Wideband Delphi Estimation Technique be used for cost estimation?

Yes, it can be adapted for cost estimation by applying the same consensus-building process to estimate project expenses.

Remember, the effectiveness of the Wideband Delphi Technique depends on factors such as the expertise of participants, a well-defined scope, and skilled facilitation.

Leave a Reply