Right, things are always probabilistic when it comes to us Humans :-) I like to think of it like Algorithm Analysis; Best-Case (estimate by the expert mentione

Right, things are always probabilistic when it comes to us Humans :-) I like to think of it like Algorithm Analysis; Best-Case (estimate by the expert mentioned above), Worst-Case (estimate by Noob who just joined the project) and Avg-Case (estimate by person who is already part of the project but is not responsible for that module). Add a fudge factor based on your reading of the circumstances and then haggle with Management. You now have a band with a upper bound and lower bound which can be realistic. PS: You may find Douglas Hubbard's How to Measure Anything: Finding the Value of Intangibles in Business useful in this regard.