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Agile Estimation: Units & Techniques

Instructor: Stephen Meyer

Stephen has worked as a Project Manager and is PMP certified, as well as certified by the Scrum Alliance.

Project requirements are one of the most important aspects of a project, but the time and effort are of equal significance. In Agile, time and effort are assigned using estimation. Learn about the units and techniques of Agile estimation.

Background

Anita's project team has consistently voiced frustration about the pressure felt from management to complete projects in predetermined time frames. The time and effort required to complete the work is decided outside of the team and this should not be the case. She is considering a switch to Agile and believes her team will support this change once they understand Agile estimation.

Project Work

The Agile approach to projects is an alternative to traditional methodologies. Instead of using a linear process and managing all project requirements together as one, Agile is iterative and incremental. It breaks the project timeline and requirements down to be more manageable. Specifically, project work is broken down into user stories, which detail functionality for specific users, as well as the reason for it.

User stories are grouped together and kept in prioritized order in a product backlog. They are estimated by the development team while in the product backlog, prior to being taken on. The user stories at the top of the backlog are the highest priority and should be taken on next. They should be in a defined and ready state and able to be given a relatively specific estimate. User stories at the bottom are lower priority and should be in a less-defined state and given a broader estimate.

Purpose

The general purpose of estimating in Agile involves planning. In the short term, it helps the team better decide which user stories to take on. Long term, different metrics involving team performance can be combined with the estimates given to allow for projections to be made. These projections are only reference points and should not be time constraints or deadlines for the team to meet.

The specific purpose of estimating in Agile is that it empowers the team. This is the appeal to Anita and her team because they are looking to have more of a voice in the project process. The Agile approach obtains input from everyone on the team because they are the individuals actually completing the work. These team-generated estimates are much more accurate than management-dictated ones.

Units

Once Anita and her team understand the makeup of the project work being estimated in Agile and the purpose of estimation, they move on to what the estimation consists of. More specifically, they first need to understand the units used for estimation. While the values used in estimation are subjective to each team, the units are consistent.

High-Priority User Stories

User stories that are at the top of the product backlog and a high priority are given a story point estimate. This is a numeric value that reflects the time and effort involved in developing and testing the user story. Since these user stories are next in line to be taken on by the team, it is important for a specific estimate to be given to them. They should be in a ready, well-defined state that makes this level of estimate possible.

The numeric values used for story point estimates typically come from a specific set of possible values. This set is a Fibonacci-like sequence where each value is the sum of the previous two values. For example, the possible values for a story point estimate would be 1, 2, 3, 5, 8, 13, 21, etc. The thinking behind it is that the difference between an 8 and a 13 is more significant and easier to define than the difference between an 8 and a 9. The intent is to create a distinction that will allow the team to reach a consensus.

Low-Priority User Stories

While user stories that are a high priority require a specific estimate, user stories that are a lower priority only need a general estimate. This is because these user stories are typically less-defined, making it harder to provide a true story point estimate. Instead, the team often assigns a size to these user stories, such as small, medium, or large and then assigns a story point estimate once the user story is more defined and a higher priority. It is helpful to associate sizes with ranges of story point values. For example, small could be 1 through 3, medium could be 5 or 8, and large could be 13 and higher.

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