Relative Estimation
Relative Estimation is an agile technique where work items are sized in comparison to each other rather than in absolute units like hours or days, providing faster and more accurate estimates.
Explanation
Humans are generally better at comparing things than estimating absolute values. Relative estimation leverages this by asking teams to compare items: Is this item about the same size as that one? Is it roughly twice as large? This comparative approach is faster, more consistent, and less influenced by individual speed differences.
Common relative estimation techniques include Planning Poker, T-shirt sizing (XS, S, M, L, XL), and affinity estimation (grouping items into size categories on a wall). Story points are the most common unit for relative estimation. A reference story is established as a baseline, and all other items are estimated relative to it.
Relative estimation works because teams can reliably judge that one item is twice as complex as another even if they cannot predict exactly how many hours it will take. Over time, the team's velocity translates relative estimates into predictable throughput, enabling accurate sprint and release planning.
Key Points
- •Compares items against each other rather than using absolute time units
- •Faster and more accurate than absolute estimation
- •Common techniques: Planning Poker, T-shirt sizing, affinity estimation
- •Uses a reference story as a baseline for comparison
Exam Tip
Relative estimation is preferred in agile because it is faster, less contentious, and more reliable than absolute estimation. Teams estimate size, and velocity translates that into time.
Frequently Asked Questions
Related Topics
Story Points
Story points are a unit of measure for expressing the overall effort, complexity, and uncertainty involved in completing a Product Backlog item, used for relative estimation rather than measuring time.
Planning Poker
Planning Poker is a consensus-based agile estimation technique where team members privately select cards representing their estimate, reveal them simultaneously, and discuss differences to reach agreement.
Velocity
Velocity is the amount of work a Scrum team completes in a Sprint, typically measured in story points, used to forecast how much work the team can handle in future sprints.
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