Cone of Uncertainty

In project management, the Cone of Uncertainty describes the evolution of the amount of best case uncertainty during a project (Construx n.d.). At the beginning of a project, comparatively little is known about the product or work results, and so estimates are subject to large uncertainty. As more research and development is done, more information is learned about the project, and the uncertainty then tends to decrease, reaching 0% when all residual risk has been terminated or transferred. This usually happens by the end of the project i.e. by transferring the responsibilities to a separate maintenance group.

From: https://en.wikipedia.org/wiki/Cone_of_Uncertainty