Hello everyone and welcome back to the Cognixia podcast. Twenty years ago, Dan Brown published his world-renowned book – the Da Vinci Code. Three years later, a film adapted from it with the same title starring Tom Hanks was released worldwide. The book and the movie both, were super interesting, and make for a great read and a great watch even today. The story takes the viewers and readers through the Louvre in Paris, stars the Mona Lisa and The Last Supper, and so many other renowned paintings, all on a quest for the Holy Grail. If you paid attention to the book or the movie or both, you would have encountered a sequence of numbers mentioned in the plot that was essential to decoding a clue that Professor Langdon is working on with Sophie. This sequence of numbers is usually written in a triangle form and is called the Fibonacci Sequence.
If you are thoroughly lost, let us explain a little more. First, what is the Fibonacci sequence?
The Fibonacci Sequence was first discussed in Europe by Leonardo of Pisa, whose nickname was Fibonacci in the early 13th century. However, the origin or the first mentions of the sequence can be traced back to about 2000 BCE in Indian literature. There is an enormous amount of literature about and using the sequence today, and it has connections to multiple branches of mathematics.
In the Fibonacci sequence, every number is the sum of the preceding two numbers, so the sequence goes 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, and so on. It is a fantastic example of a second-order linear recurrence relation.
Now, why is this Fibonacci sequence important? The Fibonacci sequence is a sort of nature’s secret code. The number of petals in a flower, the seed heads of a flower, countless paintings, plant spirals, pinecones, hurricanes, spiral galaxies in space, and so much more are examples of the Fibonacci sequence. The ratio, shapes, and arrangements formed by the Fibonacci numbers are everywhere – growth patterns of plants, arrangements of leaves, sections of your fingers, spiral shapes of sea shells, how your eye sees things, everywhere!
So, why is this Fibonacci sequence important in Scrum? What can it be used for there?
Scrum teams use the Fibonacci numbers to understand the scope and size of their product backlog items. Here, size is not just a measure of how many people are involved or how long it will take to complete the task. The size of a product backlog item involves two major components:
1. Scope
2. Complexity
Agile teams will usually not use size as an indicator of the time, the size of a product backlog item cannot be say, one day. Time is never a good indicator for estimating the size and complexity of a work item. A senior team member could finish a task in say 2 days, while a junior team member or a new team member may take 4 days. This wouldn’t be an accurate representation of size then. The size of a product backlog item should give a shared idea of the scope as well as the complexity of the work, not individual time estimates.
Developers on the scrum would regularly discuss which items to bring into the sprint. When these discussions happen, size is an essential aspect to consider so that different stakeholders get a precise idea of what to expect. So, how does one describe the relative sizes between the different product backlog items? This is where the Fibonacci sequence does the magic.