A few days ago I wrote about ranged burndown charts. Interestingly, if you track the ranges over time you end up with a chart such as the one below which corresponds to the estimating cone of uncertainty (depicted by the dashed lines). It’s interesting to note that this example includes two common occurrences that you’ll see. First, during iterations one and two the gross and net velocities were the same because no new functionality had been identified yet, resulting in an unranged estimate. Second, iteration eight had a very small net velocity because the amount of new functionality was almost as much as the amount implemented, giving a huge estimation range due to the small net velocity.