What is a story point used in Scrum?
Posted by johann | Filed under Management
Yesterday, I did a introduction class to Microsoft Team System 2010 and Scrum Template with a local Microsoft MVP Trainer, Joe Homnick . During the class, there was some discussion as to what is the difference between a story point and number of hours as it relates to scrum story. In order to clarify it for myself and potentially my team, I figured I will dump my understanding in this post.
My definition:
“Story Point is an arbitrary measure of how difficult it is to implement a story”
This assumes you understand Scrum concepts are and what a story is. If not, a quick cheat sheet for Scrum is available here.
Unit of measure:
Since the story point is an arbitrary measurement used by Scrum teams, it can use numbers or I have also seen other measurements like clothing sizes (X Small, Small, Medium, Large, Extra Large) to indicate the effort required to implement a story.
Where confusion comes in is when numbers are used. People coming from a typical Project Management (PMP) type background might immediately relate 1 story point to 1 hour of work. It is however not the case, it could be, but a story point is only a relative term.
So why use story points instead of hours?
The fact that the story points have no relevance to actual hours enables a scrum team to think abstract about the effort required to complete a story. This does create a type of effort “currency” that is different in each environment and is further defined as a team and culture around it use it.
So can story points equate to actual time spent in a sprint?
Yes, for example at the end of a 14 day sprint a team of 4 Engineers covers 56 story points.
14 days = 14 * 8 working hours = 112 hours = 448 total hours as there are 4 developers.
448 divided by 56 = 8 hours per story point.
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