How Big Things Get Done: The Surprising Factors That Determine the Fate of Every Project, from Home Renovations to Space Exploration and Everything In Between

by Bent Flyvbjerg

Define the class broadly. Err on the side of inclusion. And adjust the average only when there are compelling reasons to do so, which means that data exist that support the adjustment. When in doubt, skip adjustment altogether. The class mean is the anchor, and the anchor is your forecast.