## Sunday, May 27, 2007

### By The Book

I am actually getting somewhere with the book I am working on. Here is a small excerpt:

Consider two project teams, A and B. Each team has one project manager, four developers and three testers. Each team member makes €3,500/month and works 160 hours/month. The project managers make €4,000/month. Both teams produce 80 Story Points worth of functionality in a week.

In team A, the developers work very hard, but the testers have time to surf the Web now and then. In team B, it is the other way around. The testers are pressed to keep up, so the developers slow down a bit to avoid deluging them with more work than they can handle. On the same day, a defect is found in each project. Both defects will take eight hours for a developer to fix. What is the cost to team A? What is the cost to team B?

Give it a try. I'll publish the solution in a couple of days. (Hint: the answer is slightly less obvious than it looks.)

Anonymous said...

This got me thinking. If I know you right, I'm guessing you'll be able to show an increased cost for the bottlenecked team, probably via a calculation of the value of a story point and possibly using a calculation of an opportunity lost.

However, two thoughts enter my mind spontaneously:

1) The measure used for the output of the teams, story points, is probably not comparable across teams.
2) Does it matter if the cost is higher for fixing a defect for one of the teams, if we take the 80sp/month metric to mean that both teams consistently deliver the same amount of value per month? Isn't measuring at that level measuring at too low a level of detail.

Just a couple of quick thoughts. Looking forward to your next post.

Kallokain said...

1) The measure used for the output of the teams, story points, is probably not comparable across teams.

True. In real life, it would not be directly comparable. In this example, it just indicates that both teams deliver equal value.

(I'll rephrase the example in the book so this becomes more clear. Thank you for the input.)

It is worth noting that SP is a kind of proxy for money. You can translate SP to monetary value, but unfortunately not until after the project, and probably a maintenance project or two, has finished.

2) Does it matter if the cost is higher for fixing a defect for one of the teams, if we take the 80sp/month metric to mean that both teams consistently deliver the same amount of value per month? Isn't measuring at that level measuring at too low a level of detail.

Both teams consistently delivered 80 SP/month before the pesky defect interfered. Part of the answer lies in figuring out what happens when the defect appears.

Miscalculating the defect cost can have a direct impact on management decisions. I believe that it often does. If more angers were aware of the actual costs of defects, we would see a very different approach to project management, but we would also see large effects in line organization, and training budgets.

I'll get back with an actual answer to the problem in a couple of days.

Kallokain said...

"angers" should be "managers" of course. Sometimes my fingers do not type what my brain tells them to.

mtnygard said...

Henrik,

I am delighted to see that you are working on such a book. I have long wanted to see an application of ToC and throughput accounting to software development.

If you have not already read them, I strongly recommend the Poppendieck's books on Lean Software Development. There are obvious parallels between Lean and ToC.

Regards,
Michael T. Nygard
mtnygard@charter.net
http://www.michaelnygard.com/

Author of "Release It!"
http://pragmaticprogrammer.com/titles/mnee/index.html

mtnygard said...

Ah, I should have read further. I got too excited at the prospect of your book and posted my comment before I saw your link to Lean Software Development later on!