Translating Story Points To Hours: A Recipe For Disaster?
The practice of converting story points to hours is a common technique employed by those new to agile methodologies in an attempt to grasp the underlying concepts. However, this conversion can undermine the core principles of agile and set inaccurate expectations that are bound to cause problems down the road. By exploring the motivations behind using story points and how they differ fundamentally from time-based estimates, the pitfalls of this conversion approach become clear.
Why Translating Story Points to Hours is Problematic
At first glance, translating story points to hours can seem like a reasonable step for those accustomed to estimating projects based on timelines. However, this practice contradicts the purpose of using story points in the first place.
Story points measure complexity, not time
Story points rate the difficulty of implementing a user story. They represent the fuzziness and uncertainty inherent in software development by measuring size and complexity. Hours, on the other hand, quantify duration. While logically it may seem like more complex stories should take more time, this is not always the case in practice. Therefore, equating story points to hours makes an assumption that does not always hold true.
Velocity varies team to team and sprint to sprint
Velocity is the amount of story points a team can handle per sprint. This varies significantly between teams and even across sprints for the same team as capacity changes. By locking story points to hours, the flexibility to accommodate flux is lost. For example, a story rated as a 5 could take 10 hours one sprint and 15 hours the next. The point values stay constant while the time varies.
Sets wrong expectations on delivery
Perhaps most critically, correlating story points with hours sets unrealistic expectations around delivery timeframes. Projects estimated via story points purposefully avoid specifying timelines. However, if story points become simply surrogate hours, stakeholders expect hour-based accuracy on delivery dates. When these made-up timelines fail to materialize, trust in the team and process erodes.
The Meanings Behind Story Points
To avoid the pitfalls of equating story points to hours, it is essential first to understand what story points actually represent in agile processes. The assumptions and meanings baked into story pointing reveal why converting to hours is problematic.
Story points rate difficulty, not duration
Teams assign story points based on the relative difficulty and uncertainty inherent in each user story. Easy stories may be a 1 or 2, medium difficulty a 3 or 5, and highly complex stories an 8 or 13. The raw numeric values are less relevant than their comparative order. The goal is to gauge fuzzy complexity, not define duration.
Account for unknowns and complexity
By emphasizing comparative difficulty, story points account for the unknown factors that inevitably arise in software development. Bugs, integration issues, changes in direction – these uncertainties make predicting duration accurately impossible. Story points communicate complexity in a way that bakes in these fluid factors.
Based on team velocity, capacity
The number of story points a team accomplishes in a sprint becomes its velocity. This metric captures a teamâ€TMs capacity to take on complexity. The greater the velocity, the more story points – and therefore complexity – a team can handle. By basing estimates on velocity rather than hours, the teamâ€TMs output becomes the driver for committing to new work.
Estimating Project Timelines Without Hours
Eliminating time-based estimates from the agile planning process does not mean duration is unimportant. Rather, projections should stem from empirically-driven data analytics versus top-down assumptions. Several techniques help forecast realistic timelines even with story pointing.
Focus on velocity trends
Reviewing velocity trends over past sprints helps predict the teamâ€TMs capacity to complete upcoming user stories. If a new project contains 100 story points and velocity averages 20 points per sprint, the rough timeline becomes 5 sprints. This data-driven approach provides probable delivery dates.
Velocity predicts capacity over time
By tracking velocity session-over-session, patterns emerge on the teamâ€TMs bandwidth. Increased velocity means greater capacity to take on complexity. Decreased velocity signals reduced capacity to complete work. These trends fuel data-driven forecasts.
Alert to changes based on data
If velocity rises or falls significantly, this may alter projected timelines. By inspecting metrics rather than relying on predetermined estimates, adaptations occur based on data. The focus remains on working software over rigid plans.
Moving Forward With Story Points
Embracing story pointing requires resisting the instinct to convert to hours. Internalizing core agile values lays the foundation for fruitful estimation practices.
Embrace uncertainty
Software development will always contain unknowns. Rather than rail against this truth, bake uncertainty into the process via story points. Rating complexity and difficulty makes room for fluidity and change.
Adapt plans as new data emerges
An iterative approach means regular adaptation based on new data. If velocity slows or new complexities appear, modify scope and schedules accordingly. Transparency enables intelligent responses to change.
Prioritize value, not just delivery speed
Speed gains importance in software, but should not supersede value. Well-tested, high-quality software with the right features beats a quicker but problematic result. Story points combined with velocity analytics positions teams to optimize both cycle time and customer value by revealing capacity for complexity.
