Some of the biggest project failures (mostly on IT projects) come from our continued inability as a species to predict the future.
That statement does not sound right. Surely, that is over-generalization. So, let us start over.
Estimates of any task assume that once the work begins, there are no further decisions to be made. That it is just a matter of putting your head down and completing the task without distractions and without having to make messy decisions.
It does not work that way. Even the simplest of tasks has a million decision points. Your first beverage of the day: tea/coffee ? Do you make your coffee at home or get it at Starbucks (remember that quote from You’ve Got Mail ?) ?
We get over these decision points by creating routines in our life. Which means that you anticipate the decision points in advance and make them ahead of time. So, you don’t spend time making the decision every day, every minute of your life.
Unfortunately, routines do not work on most projects. If they did, we would not call them projects…we would call them “operations”. That means that most projects have a million decision points as well.
Decision-making is a personal thing – meaning that each individual has his/her own way of making a decision. It takes all sorts of people to make a project team. You cannot fill your team with project managers with excellent decision-making skills … you will need to leave room in your project for the nerd who cannot decide between a drop-down/list-box. There is no estimation model that can account for the time/effort involved in the decision making by all types of individuals.
All the above is not to say that projects over-shoot budgets and schedules simply because of indecisive people on the project teams. What it means, though, is that Project Managers would do well to anticipate those decision points in advance…well, atleast as many as they can.