According to the IIBA:
Relative Estimation is used to make future predictions based on past experience, knowledge, complexity, size, and uncertainty required to complete backlog items.
Relative estimation is used in Agile projects to estimate the effort required for tasks or user stories by assigning story points. Story Point is a unit of measure that the team assigns to each story in the backlog.
Five Key Areas
- Knowledge
- Experience
- Complexity
- Size
- Uncertainty
Approaches For Calculating Relative Size Of Stories
- Planning Poker
- Silent Sizing
Planning Poker
Planning Poker also known as Scrum Poker is a consensus based, gamified technique for estimating, mostly used to estimate effort or relative size of development goals. The customer or product owner reads the story and the team starts providing estimates including testing effort. Then the team discusses the story and what it will take to develop it. Then the team estimates again.
Silent Sizing
In silent sizing comparison is made between new stories to old stories to determine which are a similar size to complete ones. They help determine what story point to assign to new stories based on what was assigned to completed stories. Everyone has the opportunity to determine which stories match up and discussion occurs to reach agreement.
Strengths Of Relative Estimation
- Sizing has a positive effect on a team
- Simple
- Very adaptable
Limitations Of Relative Estimation
- Precision of the estimates might be low
- Teams’ velocity depends on how long the development team works together
- There is no one size fits all teams when it comes to story points
Agile teams use relative estimation to find out how much time and effort is needed to complete their workload during an iteration based on how long a similar task took to complete previously.
Without a good estimating system, we overrate how much we can get done. As an agile team, you want to avoid long, unpredictable planning cycles. Relative estimation is a way you can communicate when work will be delivered.
With time and repetition, relative estimation becomes more accurate which enables us to know our team’s velocity and more accurately forecast work.
