One of the most powerful tools in your arsenal for estimation as a Scrum Master is the burn up chart. At a glance it provides you with a view of the progress your team is making towards the completion of your product. It can also be used to provide estimates for completion of features or scope completed for hard deadlines.
Tracks Historical Velocity
Burn up charts are essentially a graph of completed story points versus time, or velocity, combined with a graph of total scope. This tool is only useful for projects already in flight and not as an initial project planning tool. A burn up chart only starts being accurate after the team has a few sprints under their belt. Since it uses historical data to provide an estimate of future productivity, we need to build up a history. As a rule of thumb figure around 3-4 sprints for team velocity to stabilize
As the scrum master, one of your jobs is to keep an accurate history of how many story points are completed every sprint. Burn up charts let you visualize that day in an intuitive way.
Completed vs. Total Points
A burn up chart can be used to provide an estimate of when the team will complete the work in the backlog. The total number of points is tracked right along side the number of completed points on the same chart. As the number of completed points rises it converges on the total, giving a view time to completion.
The benefit of using this approach versus a burn down chart is that scope changes are immediately visible and are not buried inside a single number. It intentionally shows the total number of points as a “moving target” that the team is trying to hit.
It goes against scrum and agile philosophy to break down and estimate the entire project up front, so what is a budding young scrum master to do? The top line, or total number of points, can be an epic, a group of epics or the entire project. It really depends on how much effort your team finds acceptable to put into estimation up front. But the point is that this number will change during the development life cycle so this chart can be used as a tool to monitor those changes.
Estimate to Completion
The burn up chart really shines through its ability to show when all the estimated stories will be completed. From the current date in the chart you can project forward to completion. By taking the minimum, average and maximum number of points completed and using those values to draw three lines projecting into the future. This will give you a window of confidence in your ability to deliver the completed product.
The maximum number of points achieved in the past gives an indicator of the best case scenario, if everything goes well then the project can be completed early. Conversely the minimum gives a worst case estimate. Finally, the average number is the probable completion date.
Note that the range can be extremely wide for large projects with completion dates far into the future. This shows the inherent uncertainly in the estimate in a way that’s easy to understand for external stakeholders.
Another neat trick we can do is estimate how much scope will be completed by a given deadline. Pick a date in the future and the chart will give you three estimates of how many story points will be completed by that date. Again it will give you best case, worst case and probable scenarios for completion.
This information can be extremely valuable in prioritizing work or changing scope in order to meet a hard deadline.
Here we can see the last sprint ended on 11/18/2017 with 112 points completed. The total number of points is 275, leaving 163 to go. How long will it take to complete? According to the chart the project will require at least 6 more sprints. It will probably be done after 9. We can be quite confident that the project won’t take more than 15 sprints. As the project progresses and we get more information this projection will become more accurate and the completion window will shrink.
Similarly if we only had 7 sprints of time left we could see that the project might be completed on time but more likely we’ll come up short. This gives the product owner a chance to make changes to the scope of the project to account for this.
Burn up charts:
- Track velocity and scope changes
- Require historical data to be accurate, the more the better
- Provide estimates to project completion
- Provide estimates to scope coverage for deadlines
- Are intuitively easy to understand
- Help product owners to plan better