Wednesday, December 07, 2005

Valued estimation

In "User Stories Applied", Mike Coen puts forward a method for estimating the cost of developing stories (or any other piece of work).

In summary:
* The development team get together with the customer.
* The customer describes a story.
* The developers quiz the customer until they are happy they understand the story.
* Each developer that wants to participate writes an estimate down.
* All developers show their estimates.
* The developer with the highest estimate states why they think it's so big.
* The developer with the lowest estimate states why they thing it's so small.
* The developers discuss the problem further until they're all happy they understand what's involved, and they estimate again.

The loop keeps going round until the team all have the same estimate, or they're happy to accept a compromise on one.

Once the stories are all estimated, they're put in a line of ascending cost and examined to make sure there are no discrepancies. If there are, then that story is re-stimated.

It works a treat, and the customers like it.

In fact they like it so much that they've come up with a variation...

Excluding the project manager, our customer team consists of two full time members and a number of people that work on our project only part-time. One slight issue is that over the last 18 months the full time members are becoming more a part of the Information Systems team and less in touch with 'The Shop Floor'. The part-time members help to ground them in the reality of the system.

On the other hand, the part time members aren't available to instantly evaluate new stories, and prioritise them accordingly.

So, once a week the customer team now get together in a 'Value and Take-up estimation'. It works in the same way as the developer estimates except the customer team are evaluating the value that a given story will add to the system, and then the take-up level expected for that part of the system in a scale of one to ten,

Obviously, the priority of a story is based on the combination of all three variables, Value / Take-up and Cost. Still, as a general rule, a story that scores high on Value and high on Take-up is going to be a story that will be prioritised very highly unless the cost is extortionate!

In fact the particular values may not be that important; there is no point discussing if a Value 8, Take-up 7 story is more important that a Value 7, Take-up 8 story on the basis of the raw values alone.

Rather it's the forum for the discussion of the values that provides the real insight, and allows everyone to have their input.

It's working to ensure that the team is working on what the whole customer team decide is the most important task, and not just the one with the loudest voice...

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