I remember reading a comment on another story which I thought was a wonderful explanation of why estimates tend to be too short: http://news.ycombinator.com/it

I remember reading a comment on another story which I thought was a wonderful explanation of why estimates tend to be too short: http://news.ycombinator.com/item?id=3522910 http://news.ycombinator.com/item?id=3522910 To quote one part: Let's say that you have 20 tasks. Each involves rolling a 10-sided die. If it's a 1 through 8, wait that number of minutes. If it's a 9, wait 15 minutes. If it's a 10, wait an hour. How long is this string of tasks going to take? Summing the median time expectancy, we get a sum 110 minutes, because the median time for a task is 5.5 minutes. The actual expected time to completion is 222 minutes, with 5+ hours not being unreasonable if one rolls a lot of 9's and 10's.