Estimation in Scrum ( T Size & Stories Points)

Absolute estimation is also called time and effort estimation in traditional project management.

Relative estimation means that instead of trying to determine exactly how long a task will take, we compare the effort of that task, to the effort for another task, and that becomes the estimate. That estimation is not done in traditional units of hours, days or weeks, instead we assign each Backlog item of value that is a relative unit or size.

T-shirt sizes:

To get started, the team simply picks one item on the Backlog that seems to be about a medium size workload, and simply calls that a "medium" in the estimate field. After that they take another item on the Backlog and compare it to the medium item they just identified, and answer the question: if that first item was a medium, what size would I give this one? The team will repeat this process on each additional item or user story on the Backlog until they're all addressed and done.

Story points:

Story points are a bit more advanced than T-shirt sizes, but the concept is similar. The first step is the same: The team picks an item as their anchor item and they'll conduct their estimations relative to that item. Instead of using t shirt sizes, this process uses what are called story points. Most teams use a famous mathematical sequence of numbers called the Fibonacci sequence. The sequence is 0,1,1,2,3,5,8,13, 21 continues on to infinity. For the sake of story points, we skip zero and the first 1. These numbers are special in that they start out close to one another, but as the numbers get higher, they spread farther and farther out. This is helpful because as the estimate gets higher, the uncertainty and risk also gets higher. This number combines both effort and risk into one number. In other words, there's not much use in debating estimation values between 21 and 25 points, but choosing between 21 and 34 is a real conversation. This concept can be tricky at first and practice is the best way to learn it to explain this concept.

Example, let's say you want to measure the effort to completely consume different kinds of fruit. You have in front of you: an orange, a strawberry, a banana, a mango, a pineapple and a cherry. What are the factors that go into that estimate? Are their seeds to deal with, do I need to eat it with a napkin? Can I eat in one bite? Do I have to peel it or do I need any tools to prepare it?

Okay, let's try it, if I choose a

Mango as our starting fruit at five points, how might you estimate the rest? I would rate them this way: Orange is three, because the peel is easier than cutting a mango.

Strawberry: one, because I don't mind eating stems; low effort.

Banana: three, because I have to peel it similar to oranges.

Pineapple 13, because it's giant, I can't eat it in one sitting.

Cherry: two. stems, seeds, you know what I mean.

It's really fun to learn how differently people have learned how to cut up a pineapple.