On estimating project tasks

Estimation is one of the most important components of project management. In my opinion it is second only to the creation of a work breakdown structure (WBS). Project schedule and costs are directly impacted by accuracy of the estimation. Whenever I bring up the subject of estimation as a topic of discussion, invariably someone will mention: “We typically end up underestimating the amount of time needed to complete tasks – especially unfamiliar tasks.” The one common theme that resonated was that everyone was reasonably confident that the tasks would be finished on time. After all, they did add safety to tasks to account for variation. So if we had safety protecting the tasks, why then do we not finish projects on time? Before we look at answering this question, let’s briefly look at the principle behind Theory of Constraints.