Wideband Delphi
A structured group estimation technique that combines anonymous individual estimates with facilitated discussion rounds.
Also known as: Delphi Method, Delphi Estimation, Wideband Delphi Estimation
Category: Techniques
Tags: estimation, planning, project-management, collaboration, teams
Explanation
Wideband Delphi is a consensus-based estimation technique that combines individual expert judgment with structured group discussion. It was developed at the RAND Corporation in the 1940s-50s and later adapted for software estimation by Barry Boehm at TRW in the 1970s.
## How it works
1. **Kickoff meeting** - The moderator presents the item to be estimated and provides any relevant documentation
2. **Individual estimation** - Each participant independently creates an estimate, including assumptions
3. **Collect and share** - The moderator collects all estimates and shares the results anonymously (typically showing the range and distribution)
4. **Group discussion** - Participants discuss the estimates, focusing on:
- Why the highest and lowest estimates differ
- What assumptions were made
- What risks or complexities were identified
5. **Re-estimate** - Each participant revises their estimate independently based on the discussion
6. **Iterate** - Repeat steps 3-5 until estimates converge (typically 2-3 rounds)
7. **Final result** - The moderator summarizes the consensus estimate and key assumptions
## Why 'Wideband'?
The original Delphi method used only written communication between participants. The 'wideband' variant adds face-to-face discussion rounds, providing a wider bandwidth of communication. This allows for richer exchange of reasoning and faster convergence.
## Key principles
- **Anonymity** - Estimates are collected privately to prevent anchoring and groupthink
- **Iteration** - Multiple rounds allow learning and convergence
- **Facilitation** - A moderator ensures productive discussion and prevents domination
- **Documentation** - Assumptions and rationale are captured alongside estimates
## Advantages
- Produces well-reasoned estimates with documented assumptions
- Reduces the influence of authority and dominant personalities
- Surfaces hidden risks and complexity through structured discussion
- Works well for novel or complex items where individual expertise is insufficient
- Produces estimates that the whole team understands and supports
## Comparison with Planning Poker
Planning Poker is essentially a lightweight descendant of Wideband Delphi, adapted for agile teams. The key differences:
| Aspect | Wideband Delphi | Planning Poker |
|---|---|---|
| Formality | High - structured rounds | Low - quick card flips |
| Duration | Hours per item | Minutes per item |
| Best for | Large, complex items | User stories, sprint items |
| Documentation | Extensive | Minimal |
| Rounds | 2-4 typical | 1-2 typical |
## When to use it
- Estimating entire projects or major phases
- High-stakes estimates that need strong justification
- When team members have significantly different expertise areas
- When detailed assumptions and risks need to be documented
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