What Is A Story Point And What Is It Good For?

What exactly is a story point? Answers to this question are all over the map. I know because I went looking.

Maybe a story point is a nebulous unit of time: “Story points represent nebulous units of time.”[7]

Maybe a story point measures effort: “Story point is a random measure used by Scrum teams. This is used to measure the effort required to implement a story.” [1]

Does a story point measure size and complexity? “So, points are relative measurements of size/complexity, not absolute measurements of duration.”[2]

Or perhaps a story point is many things: “…a story point estimate is an amalgamation of effort involved in developing the feature, the complexity of developing it, the risk inherent in it, and so on.”[13]

How are story points used? Again, opinions differ wildly. Maybe the number of story points in a sprint (velocity) is a measure of productivity: “Truth be told velocity really is a productivity measure…”[8]

Maybe story points should not be used to measure productivity: “Using story points or ideal days to measure productivity is a bad idea because it will lead the team to gradually inflate the meaning of a point…”[4]

Maybe story points should be burned down during a sprint: “Basic Truths about HyperProductive Scrum…Burn down Story points only.”[6]

Or maybe it’s the other way around and story points should not be burned down during a sprint: “I also recommend estimating the sprint backlog in hours rather than in points.”[3]

When it comes to story points, it’s a wild rumpus of opinion. Some writers believe that teams achieve steady state velocity[9], others do not[10]. Some believe that there is a mapping between story points and time[11], while others do not[12].

When I started writing this note, I hoped to answer the question in the title. After doing this research, I confess, I can’t tell any more what a story point is or what it is good for.

I now think that story points and associated practices (like burndown charts or poker planning) conflate so many intellectually distinct ideas and goals, from increasing shared understanding to avoiding gaming, that I am searching for a new way to describe them and introduce them to people who are new to Scrum.

The Scrum Guide[5] does not mention story points at all — that may be the best way to go.

[An extended discussion of this essay appears here.]

References
[1] http://agilefaq.net/2007/11/13/what-is-a-story-point/
[2] http://en.wikipedia.org/wiki/Story_points
[3] http://blog.mountaingoatsoftware.com/why-i-dont-use-story-points-for-…
[4] http://blog.mountaingoatsoftware.com/should-companies-measure-product…
[5] http://www.scrum.org/storage/scrumguides/Scrum%20Guide.pdf#view=fit
[6] Sutherland, Jeff. “Practical Roadmap to Great Scrum:
Systematically Achieving Hyperproductivity.”
[7] Khanal, Samir. “Function point vs. Story point.” See
http://c2.com/cgi/wiki?NebulousUnitOfTime for the definition.
[8] https://www.ibm.com/developerworks/mydeveloperworks/blogs/ambler/entr…
[9] http://agilesoftwaredevelopment.com/blog/jackmilunsky/significance-st…
[10] http://agilethinking.net/blog/2007/05/21/estimation-time-or-size/
[11] http://blog.mountaingoatsoftware.com/how-do-story-points-relate-to-hours
(Mike Cohn’s post)
[12] http://blog.mountaingoatsoftware.com/how-do-story-points-relate-to-hours
(Giora Morein’s response); http://radio.javaranch.com/lasse/2008/04/17/1208381586654.html
[13] Cohn, Mike. Agile Estimating & Planning.

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