Estimates (why the Map is not the territory)
I have been following JP’s musings on Project Management and Communication focusing on estimation and reporting.
For a successful technology, reality must take precedence over public relations, for nature cannot be fooled. : Richard Feynman
In my last entry I discussed the social reasons why I felt that a lot of projects miss their deadlines. Here is the setup for the scenario outlined there.
Richard Glass in Facts and Fallacies of Softwaring Engineering notes that one of the two most common causes of runaway projects is poor estimation (The other is unstable requirements)
- Estimation is usually done at the wrong time (too early)
- Estimation is usually done by the wrong people (management, architects, senior developers)
To which I would add:
- The delivery rate of any one team/project combination is a unique value that is very different to any other combination.
- No one is any good at estimating large software tasks, especially if someone else is actually going to do the work.
- No one should be estimating a software task if they won’t be involved in carrying it out.
- No one is a born estimator. It takes practice.
Many developers/development managers do not realise that “The Map is not the Territory” and , finally, few development managers really understand the above
So, when the project starts to slip, and the estimates are not being met many development managers feel that someone is doing something wrong now. They don’t realise that an error has already occurred and the results of that error have been captured into a number of documents, Gant charts and public commitments.
Tom DeMarco points out that managers often think they have the power to make people think faster by putting on the pressure. So, given that they have committed to a timetable they feel the best way to get back on track by applying pressure - to make doubly sure they make everyone think longer too by increasing the hours.
Finally, to save embarrassment, they finesse the data until they recover the lost ground…
There are better ways.