5 Reasons Why Using The Fibonacci Sequence Will Make You Better At Estimating Tasks
A critical part of managing an Agile team is estimating the time tasks will take to complete. A points system is often used to give a high-level estimate of the scale or size of a specific task. Bigger more complex tasks get more points and smaller tasks get less points. Managers can then review and prioritize tasks based upon the assigned scale.
This is where the Fibonacci scale through 21 (1,2,3,5,8,13,21) is very useful. For more on the definition and origins of the Fibonacci Sequence see our article: What is the Fibonacci Sequence? And How it applies to Agile Development.
While you could use a different scale for estimating tasks, such as 0-1 or shirt sizes (XS, S, M, L, XL), the Fibonacci scale is a better choice for 5 reasons:
1. It’s Composed Of Integers
For estimating the time it takes to complete tasks, you want a scale that is made of integers. The goal of estimating tasks in Agile is a high-level estimate. There’s no need for the granularity of 2.4 and 3.2. Integers, or whole numbers, are all that is needed. Giving the option of half-steps, quarter steps, and so on, only slows your team down in minutia.
2. It’s Exponential
When estimating time, the shorter the time span the more certainty. Longer tasks are more complex and time estimates are less precise. An exponential (grows at an increasing rate) scale provides detail for small tasks and forces uncertainty for large tasks.
Furthermore, because the Fibonacci Sequence is a lagging exponential sequence, it provides detail for small tasks (1,2,3) which are simple to estimate, but starts to provide less detail for medium tasks (5,8), and even less detail for large tasks (13,21). This forces your team to have more detail when estimating small tasks (is it a 1 of a 2?) and less when faced with large tasks (hmmm, I wonder if that is a 13 or a 21…). This helps build your estimates with increasing uncertainty as time estimates get longer, creating a more efficient, and effective estimation.
3. It Forces You To Choose “More Or Less”
In addition to building in uncertainty for increased time spans, the Fibonacci sequence also forces your team to make a choice. When faced with a larger task, “is it a, 8, a 13 or a 21?”, there is no in-between. This helps your team group and differentiate the size of tasks.
Another aspect of the Fibonacci sequence is the distance between points. 3 to 5 is a difference of 2, but 5 to 8 is a difference of 3. This allows your brain to intuitively distinguish between the numbers of the Fibonacci scale as different magnitudes.
4. It’s Non-Linear
Finally, the nonlinear nature of the Fibonacci scales reduces over-analysis. 4 out of the 6 numbers used are prime numbers, reducing your ability to evenly break down or compare tasks. Large tasks are not squarely related to one another (that’s twice as long as that), and the numbers don’t give the impression that if you just had multiple people work on it, the task would be twice as fast. This helps reduce over-analysis, or “analysis paralysis”.
5. It Sounds Cool And Adds An Air Of Legitimacy
Ok, this isn’t exactly a concrete reason that the Fibonacci Sequence is a better scale to use than others, but the word “Fibonacci” does sound cool and can help with adoption, and buy-in. The sequence is simple and easy to remember, encouraging team adoption and use. Additionally, the prestigious and somewhat mysterious nature of the sequence adds an air of legitimacy to the method, making it easier to get team and executive buy-in.
Using The Fibonacci Sequence With Your Team
To use the Fibonacci Sequence, instruct your team to score tasks from the Fibonacci Sequence up to 21.
1, 2, 3, 5, 8, 13, 21
One being the smallest easiest tasks and twenty-one being large projects.
For more one leading an Agile eLearning Development team check out our eBook guide, The Agile Guide to Agile Development. The guide contains 10 steps to transition your learning development team to Agile.
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