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I am reading about a case study about a team that estimates tasks or "story points" as they call them based on the effort needed to complete them.

What the units are these "story points" estimated in? I believe this notion of "story points" stems from a process called "agile development."

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up vote 17 down vote accepted

User stories are used in some Agile methodologies, but are not necessarily an "Agile" notion.

Stories are measured in "story points". A "story point" is the unit.

Story points measure relative complexity of a story. If one story is 2 points and another is 4 points, the latter is believed to be twice as complex/time consuming as the former.

If you do iterative development, you should be able to get a grip on how much you can complete in an iteration. If you take the ratio of story points associated with what you complete and the duration of the iteration, you have what is called project velocity: story points/iteration

Take a look at Mike Cohn's User Stories Applied for the most complete explanation of how this all works.

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Thank you! Story points sounds like a practical way to measure effort. And thanks for explaining velocity to me! – David Faux May 21 '12 at 6:11
Story points doesn't always imply 'complexity' - they could be whatever the team feels comfortable deciding/agreeing too. Complexity is the easiest and most commonly applied. Some people like to use 'ideal days' as a story point... – PhD May 21 '12 at 6:41
As you have recommended Mike Cohn's book about User Stories: His blog contains a lot of great explanations on this topic as well, see His post on "It's Effort, Not Complexity" is one of the most discussed ones on his blog and there he basically states that "Story points are not about the complexity of developing a feature; they are about the effort required to develop a feature." – datentyp Dec 20 '12 at 11:35
@datentyp - Good point. Yes, it's true that something can be very simple but still very effort intensive/time consuming--story points are indeed about effort. – Matthew Flynn Dec 21 '12 at 18:00

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