Overview
Wideband Delphi is a group-based estimation technique that combines expert judgment with structured iteration to produce accurate project estimates. Unlike traditional Delphi methods where experts never meet, Wideband Delphi includes group discussion to accelerate consensus.
Process
- Kickoff Meeting: Coordinator presents estimation task and background information to the expert group
- Individual Preparation: Experts review requirements and prepare questions independently
- Estimation Meeting: Group discusses assumptions and clarifies requirements
- Anonymous Estimation: Each expert submits estimates independently without knowing others' estimates
- Compile Results: Coordinator aggregates estimates and identifies outliers
- Discussion: Group reviews results, with outliers explaining their reasoning
- Re-estimate: Experts submit new estimates based on discussion
- Iterate: Repeat steps 5-7 until estimates converge (typically 2-4 rounds)
- Final Estimate: Group agrees on final estimate, often using median or consensus value
Key Principles
- Anonymity: Initial estimates are anonymous to prevent groupthink
- Iteration: Multiple rounds allow experts to reconsider based on group input
- Controlled Feedback: Structured discussion prevents dominant personalities from biasing results
- Expert Selection: Participants should have relevant experience and diverse perspectives
Advantages
- Reduces individual bias and anchoring effects
- Leverages collective expertise
- More accurate than single expert estimates
- Identifies hidden assumptions and risks
- Creates shared understanding among stakeholders
- Works well for complex or novel projects
- Documented rationale for estimates
Disadvantages
- Time-consuming (requires multiple meetings)
- Requires multiple qualified experts
- Can be difficult to facilitate
- May not converge if experts have very different perspectives
- More overhead than simpler estimation methods
When to Use
Ideal for large, complex, or high-risk projects where estimation accuracy is critical. Particularly valuable when:
- Project is unprecedented or innovative
- High uncertainty exists
- Multiple technical disciplines are involved
- Stakeholders need high confidence in estimates
