Tasking developers with creating detailed estimates is a waste of time (2020)
An estimate is usually the sum of a bunch of smaller estimates. Those estimates have a probability distribution that is asymmetric. While sometimes they can be quicker than anticipated, the lowest they can go is zero (turns out we don&#x27;t need it, cut it) and that kind of thing is relatively less common than a blowout the other way. Those blowouts are uncapped, while zero time is a minimum there&#x27;s no maximum. The unknown unknowns are the things that get you. Seems like it will take X but the frobnicator was broken in ways we couldn&#x27;t have anticipated so we had to get a different thing and then hack it to make it do what we actually needed etc etc. Each individual item has a low probability of that happening to some extent. When you have a bunch of things in sequence one of them probably will if not more.<p>IIRC each item is described by a poisson distribution. (Have I got that right, mean, long tail). Nobody models estimates as a sequence of dependent, poisson distributed events, that I&#x27;ve heard of at least. If you did you might at least get a range on the estimate. Between 2 and 20 days. That would be more accurate. Useful to anyone much? Unclear.