Environment And Load Factor

AlistairCockburn comments about the impact of environment on LoadFactor:

But that is also taking into account your environment, that people are PairProgramming and have an unnamed partner while programming, and will themselves be partners in programming. That partnering is not written on the board and is somehow magically folded into the LoadFactor, no one knows exactly how, which is why LoadFactor is JustaNumber?. It only works in your context for your specific use of it, which is to tell how long something will take your team when they write an estimate on the board. It doesn't necessarily work backwards and it doesn't necessarily work in different contexts and it doesn't work to map other people's logged programming hours to XP staff logged programming hours. --AlistairCockburn

Of course it is taking our environment into account. Our programmers convert ideal estimates to ideal work in 2.5 days for every ideal day. Since they report in ideal days, it certainly follows that out of 15 days in an iteration, they spend 9 doing something that is NOT recorded as work on one of their tasks. It's a good bet that it is made up of partnering with other people, work on non-tasks, reading, wasting time, etc.

It remains true that if we have a project estimated (by our programmers) as requiring 1,000 ideal days, it will take them about 2,500 real days to do it. It would be nice to know why it's 2,500 and not 2,000 or 3,000, but it isn't necessary to know to do the math.

Am I missing something?

" it certainly follows that out of 15 days in an iteration, they spend 9 doing something that is NOT recorded as work on one of their tasks" This would only follow if you measured time spent "working on tasks". It is equally reasonable to suppose that they spend only half the time on the tasks that the LoadFactor would indicate, or twice.

But Kent, we DO measure time spent working on tasks. Denny, nee Bob, asks them for IPT done and IPT to go several times an iteration. They are supposed to answer in the same terms as the original IPT estimate. --R

However, Alistair, you seem to be saying that using IdealProgrammingTime and LoadFactor together is C3-specific or ExtremeProgramming-specific. I don't agree at all. People have been doing this (albeit under different names) for decades. I can remember laughing at a manager when he joked about multiplying estimates by two and then moving up the next higher units. I can also remember my chagrin when my next publicly announced two day task took me four weeks.

I can easily believe that "2.5" is project specific, but the estimation method certainly isn't.

--KentBeck