Estimation in the context of agile development typically falls into two broad categories: Size Estimation and Effort Estimation. Each category has its own methods and techniques for facilitating, and specific prerequisites and success criteria.

Size Estimation:

Size estimation focuses on quantifying the relative size or complexity of items in the product backlog. This helps teams understand the scope of work and make informed decisions about prioritization, planning, and resource allocation.

1. Story Points:
   • Facilitation: The team assesses the relative size of backlog items, usually using the Fibonacci sequence (e.g., 1, 2, 3, 5, 8) to assign story points.
   • Prerequisites: A clear understanding of what a “story point” represents in the team’s context and an established reference story.
   • Success Criteria: The team reaches a consensus on story point assignments, providing a common basis for understanding the size of backlog items.
2. T-Shirt Sizes:
   • Facilitation: Items are categorized into T-shirt sizes like S (Small), M (Medium), L (Large), or XL (Extra-Large) based on their relative size and complexity.
   • Prerequisites: An agreed-upon definition for each T-shirt size, and alignment on how the sizes relate to the team’s capacity.
   • Success Criteria: The team agrees on the size categories for each item, making it easier to prioritize and plan work.

Effort Estimation:

Effort estimation involves estimating the amount of work, time, or resources required to complete backlog items. This helps teams with scheduling, capacity planning, and resource allocation.

1. Ideal Days:
   • Facilitation: Team members estimate how many “ideal days” it would take to complete each backlog item. An ideal day is typically an uninterrupted, distraction-free day of work.
   • Prerequisites: Consensus on the definition of an ideal day and an understanding of the work environment.
   • Success Criteria: The team reaches a collective estimate of ideal days for each item, enabling better planning and capacity management.
2. Planning Poker:
   • Facilitation: Team members use planning poker cards (e.g., Fibonacci sequence) to anonymously estimate the effort required for each item, followed by discussion and re-estimation if necessary.
   • Prerequisites: Planning poker cards or a digital tool, and a shared understanding of the chosen estimation scale.
   • Success Criteria: The team converges on a consensus estimate for each item, enhancing predictability and planning accuracy.
3. Hours or Days:
   • Facilitation: Team members estimate the effort in hours or days, providing a more granular view of the work required for each backlog item.
   • Prerequisites: A common understanding of the hourly or daily estimation scale, and a clear definition of a “day’s work.”
   • Success Criteria: The team agrees on the effort in hours or days for each item, facilitating detailed scheduling and resource allocation.
4. Comparative Estimation (High-Low):
   • Facilitation: Items are compared to known reference items (high and low complexity) to estimate their relative effort.
   • Prerequisites: Well-defined reference items with known effort, and a shared understanding of how to relate items to the references.
   • Success Criteria: The team successfully assesses the relative effort of backlog items using the references, providing a basis for prioritization and planning.

Success Criteria for Both Categories:

1. Consensus: The team reaches a consensus on the estimation for each backlog item, ensuring shared understanding and commitment.
2. Predictability: The estimations enhance the predictability of work delivery, allowing for more accurate planning and release forecasting.
3. Transparency: The estimation process is transparent, enabling stakeholders to understand how items are prioritized and scheduled.
4. Re-Estimation: Estimations are regularly reviewed and updated based on actual progress and evolving knowledge.
5. Improved Planning: Estimations help improve planning, allowing teams to allocate resources effectively and deliver value to customers.
6. Alignment: Estimations ensure alignment between team members and stakeholders regarding the scope and effort of work.

The choice of estimation technique depends on the specific needs of the project, team preferences, and the granularity required for planning and decision-making. Success in estimation lies in the ability to provide valuable insights, promote transparency, and support effective resource allocation and work prioritization.