Firstly what are the 3 points? Simply the best case, the worst case and the most likely. Just like when you ask how long the repair work will last and you get the reply - "I think it'll take 5 days but if we're lucky it could be 4. Or maybe it'll be much more difficult than I think. It might even take 10 days if there are unexpected difficulties."
In this case the person carrying out the work has given you more information than simply saying it'll probably take 5 days. We have a handle on the anticipated risk associated with this task. The risk associated with the estimate is captured in the gap between best and worst cases. A very wide range shows that he really has no idea how much effort is required for that
The nice thing about giving xProcess 3PE's is that it give you back 3 potential end dates - the 50% end date (you're as likely to finish by then as to overrun), the 75% e…