Traditionally software teams offer estimations in a time format (days/weeks etc.), recently teams have moved towards story points. They use the Fibonacci format (0, 0.5, 1, 2, 3, 5, 8, 13, 20, 40, 100) to gauge the relative effort of work required. Although it sounds somewhat odd, using this system has been shown to be helpful, because it requires the development team to make tough decisions related to the difficulty of work.
Here are few reasons to use story points:
- Dates don’t account for the non-project related work that inevitably creeps into our days: emails, meetings, and interviews that a team member may be involved in.
- Dates have an emotional attachment to them. Relative estimation removes the emotional attachment.
- Each team will estimate work on a slightly different scale, which means their velocity (measured in points) will naturally be different. This, in turn, makes it impossible to play politics using velocity as a weapon. (Scrum.org, 2014)