Why Story Points Are Not Hours: A Comprehensive Analysis

Estimating the effort required to complete tasks is an essential aspect of project planning and execution. In the context of agile development methodologies like Scrum, story points have emerged as a popular alternative to traditional hour-based estimation techniques. Story points provide several advantages over hours when it comes to estimating the complexity and effort required for completing requirements. This article explores the reasons why story points, rather than hours, are used for estimating in Scrum teams.

Different Rates of Work

One key limitation of mapping story points to hours is the inherent variation in team members’ rates of work. Individuals within a team may have different levels of skills, experience, and productivity. When story points are converted to hours using a fixed equivalence (e.g., one point equals eight hours), it becomes impossible for team members with different work rates to agree on estimates. This discrepancy can lead to inaccurate plans and hinder effective collaboration within the team [1].

Relative Estimation

Story points, on the other hand, are a relative unit of measure used by Scrum teams to provide estimates of effort. Rather than estimating in hours, teams consider how much effort a product backlog item will require relative to other items. This approach of relative estimation makes the process easier and allows for a consensus among team members. By focusing on the relative complexity of tasks, teams can avoid the pitfalls of trying to convert abstract concepts into concrete time units [2].

Accuracy and Flexibility

Story points offer a more accurate and flexible measurement technique compared to hours. They eliminate the correlation with the skills and experience of a particular individual estimator, as story point estimation is a universal measurement across the entire team. This approach ensures that the estimates are not biased by individual differences and instead represent a collective agreement. Furthermore, story points enable the tracking of velocity, which is a capacity planning method that demonstrates how much product backlog effort a team can handle in one sprint. The ability to track velocity provides flexibility in planning and release deadlines, as changes in velocity do not necessitate re-estimation [3].

In conclusion, story points offer distinct advantages over hours when it comes to estimating effort in agile development. By considering the different rates of work within a team, embracing relative estimation, and providing accuracy and flexibility, story points enable more effective planning and collaboration. Scrum teams can benefit from adopting story points as a means of estimation, leading to better project outcomes and improved productivity.

Sources

  1. Mike Cohn. “Don’t Equate Story Points to Hours.” Mountain Goat Software. Available at: https://www.mountaingoatsoftware.com/blog/dont-equate-story-points-to-hours
  2. Scrum.org. “Why do we use Story Points for Estimating?” Scrum.org. Available at: https://www.scrum.org/resources/blog/why-do-we-use-story-points-estimating
  3. RubyGarage. “3 Reasons to Estimate with Story Points.” RubyGarage Blog. Available at: https://rubygarage.org/blog/3-reasons-to-estimate-with-story-points

FAQs

What are story points in Agile development?

Story points are a relative unit of measure used in Agile development, particularly in Scrum, to estimate the effort required to complete product backlog items. They provide a way for teams to assess the complexity and size of work items without directly equating them to specific time durations.

Why should we not equate story points to hours?

Story points should not be equated to hours because it fails to account for the different rates of work among team members. Mapping story points to fixed hour equivalents can lead to inaccurate plans and hinder effective collaboration within the team.

How are story points estimated?

Story points are estimated using a relative estimation technique. The team compares the effort required to complete a particular item relative to other items in the product backlog. This approach allows for a consensus among team members and avoids the need to convert story points into specific time units.

What are the advantages of using story points over hours?

Using story points instead of hours for estimation offers several advantages. Story points provide a more accurate and flexible measurement technique, eliminating the bias introduced by individual differences in skills and experience. They also allow for tracking velocity, which helps with capacity planning and release deadlines. Additionally, story points make estimation easier and enable effective collaboration within the team.

Can story points be converted into hours?

While story points can be converted into hours, it is generally not recommended. The conversion undermines the benefits of relative estimation and fails to account for the variation in work rates among team members. It is more effective to use story points as a relative measure of effort rather than trying to convert them into specific time units.

How do story points contribute to agile planning?



Story points contribute to agile planning by providing a common understanding of the effort required for completing product backlog items. They enable teams to estimate the relative complexity and size of work, which helps with prioritization, capacity planning, and making informed decisions about what can be achieved within a given timeframe.

What is the relationship between story points and velocity?

Story points and velocity are closely related in Agile development. Velocity is a measure of the amount of work a team can complete in a sprint. By tracking the number of story points completed in each sprint, teams can calculate their velocity. Velocity helps with capacity planning, forecasting, and evaluating the team’s productivity over time.

Are story points consistent across different Scrum teams?

Story points are not consistent across different Scrum teams as they are a relative measure specific to each team. The scale used for story point estimation may vary from team to team, but the relative comparison of effort remains consistent within a particular team. It is important for each team to establish their own baseline for story point estimation to ensure accurate planning and communication.