Project managers often use a combination of both top-down and bottom-up estimation techniques. They start with top-down estimates during the project initiation and planning stages to get a broad understanding of the project's feasibility and scope. As more information becomes available, they refine the estimates using a bottom-up approach for greater accuracy. This iterative process helps ensure that project estimates are as realistic and precise as possible.
As a project manager, by proactively accounting for uncertainty, you can minimize the impact of unexpected events on your project and increase the chances of delivering successful outcomes. Remember that uncertainty is a natural part of project management, and your ability to adapt and respond to it is a key skill for an IT project manager.
Three-Point Estimation is a valuable tool, especially for complex and uncertain tasks. However, it's important to use your judgment and experience to interpret the results and make informed decisions based on the estimates.
On any project, task estimation is both an art and a science. It's essential to consider various factors and involve the right people to arrive at the most accurate estimates possible.