Common question
“How long will this take?” is an extremely common question, and is equally commonly dreaded.
Requirements for estimation
Doing estimation perfectly requires a detailed understanding of the problem, a solid intuition for probability and statistics, and carefully navigating a whole bunch of uncomfortable feelings and complicated social pressures in order to make good trade offs.
2 key criteria: large and certainty
The core problem that we’re going to talk about is that estimation (deliberately, and correctly) combines two quite different things: How large a task is and how uncertain you are about that, and that depending on what problem you’re actually trying to solve, you need to combine these in different ways.
Uncertainty
For example, consider the questions “How long will this typically take?” and “How long might this take if things don’t go as smoothly as expected?”. These obviously have different answers.
It’s ok to not do it
Another reason you might stop here is that if the task is still worth doing if takes as long as your 99%-ile, the task is obviously worth doing and you might was well just do it.
Three point estimation
There’s a technique called three point estimation that lets you take your median and 99%-ile (and a best case estimate) and gives you a mean.