Story Points Fibonacci sequence as scale of estimation. Why use Fibonacci sequence or Fibonacci series for Story Points in a agile scrum t
Introduction
The use of the Fibonacci sequence as a scale for estimating and sizing story points is a prevalent topic in Agile Scrum teams. This article addresses the frequently asked question of why the Fibonacci sequence is chosen for story points in an Agile Scrum setting.
Need for Estimation - Predictability
"When will you deliver the project?"
"How can you ask that question? We are Agile."
Predictability stands as the paramount reason for estimation in a project. With finite resources such as budget, time, and team members, predictability becomes crucial for delivering maximum outcomes within the available constraints.
What is a Story Point?
Story points serve as a unit for estimating the 'Size of Work' during story estimation. These points are team-specific and represent an imaginary unit. Various number sequences, including the Fibonacci series, are used for estimating story sizes.
Story Points Scale
Agile estimation involves abstract units, and various number sequences are used for this purpose. The Fibonacci series, modified Fibonacci series, power to two, series of five, T-shirt sizes, and other creative scales are utilized.
What is the Team Velocity?
Team velocity, a key outcome of story point estimation, represents the average of past sprints. It aids development teams in committing to work and assists product owners in budgeting and forecasting. Consistent velocity indicates a consistent throughput by a team.
Benefits of Using Fibonacci Sequence for Story Points
Natural Rhythm
The Fibonacci series, occurring in nature as Fibonacci numbers, aligns with a natural rhythm. Its progression reflects a harmonious and naturally evolving sequence.
Fibonacci Series Resembles Product Backlog
In a product backlog, stories at the top are more refined, mirroring the increasing gaps in the Fibonacci series. This granularity mirrors the principle of "being roughly right over being precisely wrong."
Problems Don't Grow in Sequence
Problems vary in size, and the Fibonacci series captures this non-linear growth. It discourages assuming that a problem is exactly double or triple the size of another, promoting more accurate estimation.
Humans Are Bad at Estimation but Good at Comparison
Human estimation skills excel in comparison rather than precision. The Fibonacci series, with its relative sizing, accommodates this human tendency and is more effective than linear scales.
Accurate Estimate is Oxymoron
The concept of an accurate estimate is challenged, as precision is often unattainable. The Fibonacci series embraces the idea of estimating within a range, aligning with the Cone of Uncertainty in project management.
Law of Large Numbers
The law of large numbers suggests that, over a large number of stories, variations in estimates tend to balance out, providing a more accurate aggregate. This principle helps in minimizing the impact of individual estimation errors.
Faster Estimation Using Poker Game for Story Pointing
Story pointing through poker games encourages group ownership and quicker consensus building. The ranges in the Fibonacci series facilitate faster decision-making, avoiding prolonged arguments over precise numbers.
Disassociate From a Formula
The Fibonacci series disassociates from a specific formula, reducing psychological attachment to numerical scales. This detachment helps teams focus on relative sizing without fixating on formulaic approaches.
Disadvantages of Non-Numeric Scales
While non-numeric scales like T-shirt sizes or physical relationships may be familiar, they lack comparison units and even distribution. The Fibonacci series, with its numerical sequence, outperforms non-numeric scales in reflecting backlog granularity.
It's Easy and Fun
Story pointing with the Fibonacci sequence is simpler and more enjoyable compared to traditional estimation techniques. Once understood, it becomes an easy and fun method that promotes collaborative decision-making.
In conclusion, the Fibonacci sequence offers a range of advantages for story point estimation, aligning with human psychology, nature, and the dynamic nature of project complexities. Its ease of use and adaptability make it a preferred choice for Agile Scrum teams.