Agile Estimation

Estimation in Agile tends to land in two camps:

1. those that want to estimate work items as a means to roughly predict what is going to happen during a Sprint whilst Sprint Planning for example
2. those that focus instead on the exhibited flow by measuring the Cycle Time at periodic intervals of how many uniform sized work items are completed when implementing the Kanban Framework for example.

This article addresses the former situation when a forward predictive estimate is needed.

Story Points

This approach of using abstract units of measure for estimates often causes quite a bit of confusion especially if teams are conditioned to use time based estimates.

Story Points are used to indicate the size of effort or complexity associated with a User Story or work item in terms of the amount of effort to complete it to a potentially shippable, or done, done, done state. They are abstract, in that, they do not relate to time but instead are a magnitude of effort needed to complete a work item.

Story Points as a Unit of Measure

When using Story Points with User Stories for example, metrics such as the Velocity show the total number of Story Points on completed User Stories for a Sprint, or more plainly, how much work was done in a fixed time period.

Story Points then become an indication of how much work is attributed to a work item, or User Story.

Relative Sizing

Using an abstract measure such as Story Points to provide an indicator of effort tends to work best when work items or User Stories are compared and can be sized relative to each other. For example, a work item or User Story can be sized relative to another by asking simple questions such as "is this more or less effort than the other item?" and "is this item twice or 3 times more effort than another item?".

With relative sizing, the first item to be sized is the hardest as it then sets the benchmark for others relative to it. Hence, it is recommended to initially find a work item that is a small size that can then be sized and other items sized relative to it.

As more items are sized then the Story Point sizes begin to normalise and it gets easier to size additional items as there are more to compare them to.

Techniques

• Planning Poker is a basic technique that allows a team to provide a detailed estimate based upon a holistic approach to complete a work item. This technique can be a little slow when compared to others.
• Affinity Sizing is a simple technique that allows a quick rough estimate to be provided, and is useful is a large number of items are needed to be estimated quickly such as when initially creating a Product Backlog for example.

See Also

• Agile Metrics
• User Stories
• Scrum Framework
• Sprint Planning & Product Backlog Refinement
• Cycle Time
• Kanban Framework