Clarification (re: illusion of predictability)
What I wanted to say with my previous post was that you can’t accomplish anything but ballpark estimates (although acknowledging this fact and measuring how “off” your estimates are can, over time, make your estimates better) and that this is something everybody must realize – from programmers to project managers and customers.
After accepting this fact, one must strive to achieve the highest possible level of predictability. My point is that this won’t happen until planning is done in a manner that is acknowledges the unpredictability of estimates.