The estimation is a sensitive topic. In traditional projects, the estimation is absolute and based on the precision.
In Agile project, it's a revolution in the mind: the estimation is no more absolute but relative, and based on accuracy. Relative? But relative to what? The estimations is based on the Fibonacci number sequence (1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, …).
Ok, I guess now you have three W questions: When, Who and Why? The answers are short too:
- When? Anytime
- Who ? The development team
- Why ? For the planning
In which units do we estimate the work? Well, it depends. For the Product Backlog, it's in points. But for the Sprint Backlog tasks, it's in hours!
Well, now let me introduce three estimation methods:
- the poker directions,
- the estimation of the first of five,
- the estimation in t-shirt size.
The poker directions
The Product Owner explains the story.
Then each team member selects a card without showing it.
Once all member has selected a card, all the members show their card.
Now, let's launch the discussions. The members with the highest and the lowest estimations explain their choice. If needed, the Product Owner can give additional information.
If a consensus is reached, the team do it again.
The value of the chosen card is the point of the task.
The estimation of the Fist of Five
This method is very easy. Each team member gives a mark of each story :
- 1 : I'm opposed
- 2 : I have reservations
- 3 : I can support.
- 4 : Good idea
- 5 : I love it
And this mark is the points of the task.
The estimation in T-shirt size
The method of estimation in T-shirt size is a little more complex. There are three steps.
For the step 1 (1 min duration), you have to make agree the team on requirements of different sizes:
- a Small requirement ("S"),
- an eXtra Small requirement ("XS"),
- a Medium ("M"),
- a Large ("L"),
- an eXtra Large ("XL"),
- an Epic.
In the step 2 (10-30 min duration), ask to the team to split the remaining user stories into the categories (XS, S, M, L, XL and Epic). Then review it.
In the step 3 (10-30 min duration), let the team adjust the categorizations. Then review it.
Now the Product Owner and the developers should discuss about the items that have difference sizes. In case of conflict, the team can decide.
At the end, a value of points is given to each ticket depending on the T-shirt size ("quantification"):
- for the User Stories (at the Sprint level):
- XS : 1 point
- S : 2 points
- M : 3 points
- L : 5 points
- XL : 8 points
- for the Epics (at the Release level): 13, 21, 34
- for the Features (at the Roadmap level): 55, 89, 144