alt Hacker News"Deliver working software frequently, from a couple of weeks to a couple of months, with a preference to the shorter timescale."
"Working software is the primary measure of progress."
"At regular intervals, the team reflects on how to become more effective, then tunes and adjusts its behavior accordingly."
None of which requires estimates. And the bit about working software as the primary measure of progress is specifically targeted against the estimate-driven culture of the time, where people would treat GANTT charts, "percentage complete" numbers, etc, as meaningful measures of progress.