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by Martin Fowler.
Original Post: Bliki: StoryCounting
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Feed Description: A cross between a blog and wiki of my partly-formed ideas on software development
Story counting is a technique for planning and estimation.
Similarly to StoryPoints it works with
XpVelocity to help you figure out how many
stories you can deliver in a fixed period of time. It differs,
however, in that you just consider the number of stories per unit of
time and (mostly) ignore their relative sizes.
The rationale for story counting comes from experience. I've
heard several teams look at their history and find that over the
course of the project, their estimates from using story points are
no more accurate than if they had simply counted how many
stories were in each iteration. Given that, the effort of
calculating story points isn't worth doing.
Using story counting does not imply that all the stories are
roughly the same size (although some teams do work that way).
Stories can still vary in size, but over time the bigger and smaller
stories will cancel each other out, hence a simple count ends up the
same.
This doesn't mean that you discard all consideration of relative
size. Teams usually put enough effort in to ensure that the stories
are within an order of magnitude of each other in terms of effort
(so if they were given story points, they would be in a 1-8 point
range). [1]
With story counting, you use velocity in much the same way as usual,
the only difference is that velocity is just a sum of stories rather
than a sum of story points.
One of the benefits of estimating with story points is that it
helps identify poorly understood stories. So when using story
counting you need to ensure there is some mechanism to spot
stories with hidden blobs of complexity.
So far the teams I've come across using story counting are teams
that have already been good at using story points, so it may be that
story counting is a technique for more advanced teams. I've found
teams work well with both story points and story counting and have
no preference between them.
1:
There's still a danger that you can get into difficulty by
doing all the small stories first, thus getting a false picture of
progress. If you're concerned about this you can do a rough sizing
of stories (such as "T-shirt sizing" into Small, Medium, Large, and
Extra Large). Unlike Story Points, don't worry about the proportions
between the sizes, all you need is to look to see if there are
imbalances in the distribution of stories over time, such as all the
extra-large stories at the end.
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