Think of estimation as an outer bound (with a confidence level). You are saying "I am 98% sure the project will be completed by time X." The more unknowns you h

Think of estimation as an outer bound (with a confidence level). You are saying "I am 98% sure the project will be completed by time X." The more unknowns you have, the farther out you should push the deadline. Give yourself extra time: no one will complain if you finish early.