In scrum, story points are a numerical way of estimating the effort required to complete a user story. When adding new stories to the backlog, scrum masters will often use the Fibonacci sequence (1, 2, 3, 5, 8, 13, 21, etc.) to determine the effort required. But why? What are the advantages of using the Fibonacci sequence for story points? Let’s take a look.
The Fibonacci sequence is a great way to estimate story points because it accommodates for the uncertainty that comes with any estimation. When we estimate using numbers like 1, 2, or 3, we tend to be overly optimistic because we round down the true effort required. This can lead to problems later on when the story is actually being worked on and takes longer than expected.
Fibonacci sequence forces you to be more precise in your estimation. With numbers like 1 and 2, it’s easy to say that a user story will take “about an hour” or “a couple of hours.” But when you get to numbers like 13 or 21, you’re forced to be more specific. Is it 13 hours? 21 hours? 2 days and 1 hour? This precision is important because it allows you to better plan your sprints and manage your time. For example, if we think a story will take 8 hours to complete, we have to use the number 13 instead of 8. This may seem like a small difference, but it can make a big impact in the long run.
The Fibonacci sequence encourages you to think in terms of relative size. When determining the effort required for a user story, it’s often more helpful to think in terms of how much larger or smaller it is in comparison to other stories. Is this new story three times as large as the other one? Or five times as large? The Fibonacci sequence makes these comparisons easy by providing a set of numbers that increase exponentially.
Using the Fibonacci sequence for story points can help reduce bias and improve accuracy. When we estimate how long something will take us, we’re often guilty of anchoring bias – that is, we base our estimate on the first number that comes into our head and then adjust up or down from there. For example, if I’m thinking about a user story that might take me two hours to complete but I know I can probably do it in one hour, I might anchor my estimate at two hours and then adjust downwards to one hour. By using the Fibonacci sequence, we can avoid this bias by starting with numbers that are far from what we’re thinking about – like 13 or 21. This forces us to really think about the size of the user story and come up with a more accurate estimate.
In addition, the Fibonacci sequence is a great way to encourage discussion and collaboration within the team. When estimating using the Fibonacci sequence, team members are forced to discuss and justify their estimations. This can help uncover potential problems and roadblocks early on before they have a chance to cause problems later.
Fibonacci sequence for story points in scrum helps to ensure precision in estimation, allows for easy comparison of sizes between user stories, and reduces anchoring bias which can lead to inaccurate estimates. All of these factors contribute to a more successful and effective scrum process. So next time you're estimating user stories, consider using the Fibonacci sequence!