Estimations

I remember the first time I heard about Delphi Estimation*. It was my first undergrad course on software engineering. I couldn't stop laughing for a while, how can you base the whole project plan on some persons guess? It sounded so stupid, I kept making jokes about it for a while.

Many years later I found my self having a great deal of respect for estimations based on experienced persons "guesses". Delphi method just growed on me, without me even noticing.

I can now see at a proposal and just know if the estimates are good or not, by heart, I just know. During the last decade I acummulated experience and I am able to classify requirements by risk, know what can be done fast and where the programmers are being just too optimistic, in mi head in minutes.

But this gut feeling wasn't given to me by the gods as a gift, it was built with hard work. I have records of times of the work I have done, for years. Every day I record how much time I spent in each project or activity. Not histericaly, with seconds, but just a rought count each day. Every month I take an hour to summarice it and check if my estimates were correct when I planned my activities. Some times my estimates where acurate, some times they weren't. I learned from the mistake and managed to improve my estimates for next month.
I then started doing the same thing with other's people's work. I created a way to classify requirements by complexity (a personal simplification of the function points, that latter learned, are called use case points). I used to estimate how much time a team needed to develop a set of classified requirements. Then I measured, and compare my "guess" to reality and learned from the mistake. I made this for years and still do it, every day, even with the smallest simple task (like checking expenses from a trip, or reviewing a report).

I learned this wonderfull trick in the same class where I learned the Delphi method. I was "forced" to used the PSP (Personal Software Process) that includes keeping an engineering journal with notes of your work and time taken by different activities. My journal was then a ridiculously pink Hello Kitty notebook, now I just keep it all in google docs files. I will record in a while that this post took me about 40 minutes to write (including finding the magic eight ball picture), and hope that after the 5 minutes it took you to read it, you are curious enough to check the PSP and keep a journal. Believe me, its worth every second spent on it.


* Sorry about including a Wikipedia link as a reference, couldn't find a better link to explain the Delphi Estimation. If you have a better reference, please let me know, I will gladly replace the link.