Random Thought – User story sizing

User story sizing is based on relative sizing. It means story-A is approximately twice big as of story-B and your big is different from mine.  It means there is no standard way of saying that how much resources (skill, time, people, coordination effort, etc.)  are needed to complete a story.

But there is a catch. As we start working together, slowly your big and mine big start to converge. But it requires a close working relationship. It also means that team-1 big might be different from team-2 big, so we can’t compare team-1 and team-2 on the basis of the number of story points completed in a sprint even if team size, type of work, the skill set of team members, distribution, and other thigs are same.

To compare teams, we need to look into their velocity trend with annotated information around context for each team (number of team members, type of work, distribution of team members, the skill set of team members, the dependency of stories, availability of team members, the structure of stories, etc.). Also, every spike (and dip as well) in trend line should be annotated with reasoning (e.g. team lost few members during sprint five).

Now, let’s back to assigning story points to each story. We as human beings are terrible at sizing, especially if size is either big or small. So any scale which is to be used for sizing user story should be widely spaced and space between two pin points must keep on increasing as size increases (assuming we will not estimate the small work). Fibonacci series fit into this requirement. It is suggested that every team member develops some mental model to start with for sizing purpose. I have developed mine own model and love to share:

Story Point	Mental Model	Remark
1		Story is too small to estimate, it must be combined with a similar story.
2		Story is small but acceptable to work with.
3		Story is of good size and I can complete the work in a couple of days.
5		Story is again good size but may touch upper limit of my capacity to complete in a couple of days.
8		Story is big enough. I need to split into smaller ones so I can complete the committed work in a couple of days.
13		Story is definably big and must to be split into smaller ones. Are we going to the moon?
21		Oh my God! It is not a story. It is an intergalactic ship.

On the basis of this mental model, I have also created planning poker cards which are available at https://github.com/tusjain/agileanswer/blob/master/PlanningPoker/PlanningPoker.pdf under common creative license.