When Burn down charts don’t tell the full story
Burn down charts are one of the artefacts used in Agile projects frequently. However burn down charts have limitations. In this article, I am going to look at scenarios – when burn down charts fail to tell the full story?
Burn down charts
Burn down charts show the status of remaining quantum of work. The quantum of work is shown on the Y-Axis whereas the timeline is shown on the X-Axis. This is simple yet effective visual representation of project progress, as shown below:
As you can see, I have used quantum of work in days. However, we can use story points or any other unit as well. It’s an easy to use chart and it tells the story visually. This chart, above, is for a sprint of 4 weeks.
Creating burn down chart
I have used Microsoft Excel to create the burn down chart. Excel provides the maximum flexibility, however other tools like JIRA can also do the same.
For this post, I have used an e-commerce project to create this burn down chart. The chart is created using the following backlog tracking sheet:
This is a snap shot of the data. The total number of estimated days for this project is 56 days and the release date is 28-Feb-2017.
Limitation of burn down chart
Burn down is a nice and simple chart but has limitations. These limitations are as below:
- It shows the work progress from backlog perspective only
- It does not show the impact of scope changes
To understand it, let’s look at our burn down chart.
If you look at the burn down chart above, there is a steep down slope in the chart from 27th Feb (As indicated in the image below). So what happened here? Was this a heroic effort by the team to finish everything on the last two days?
This is one of the limitations of the burn down chart. In this scenario, how would we find out what happened? This is where burn up charts help.
Burn up chart
Burn up charts shows the amount of work completed in the project over the period of time. This means that it shows the info, which burn down charts don’t. This makes them perfect foil to each other.
A burn up chart is shown below.
The Blue line shows the total amount of work in the project. Saffron line shows the work completed in the project. Both the curves converge, if there is no change in the scope, as shown in the diagram.
Now let’s consider our case of e-commerce project. The sprint burn down chart showed a steep curve for the last two days. What was the reason? Let’s see the burn up chart for the same sprint.
As you can see now that the estimated work or Total work curve has an upward slope between 10th and 18th. This clearly shows that there was change in the scope of work and it was not because of heroic effort of the team.
Another scenario of limitation of burn down chart
Let’s take another example of limitation of a burn down chart. Have a look at the burn down chart of a project.
Was the team not working after 19th July or there was something wrong here? This is not so obvious looking at the burn down chart. So let’s put them together.
What do these two tell us? The team is making progress at the desired velocity yet the there is no reduction in the backlog. That’s because, the scope of work is increasing at the same rate.
You can see the gap between the scope of work and the work done remaining the same throughout (in the burn up chart).
Well this is an exaggerated scenario but good one to make the point that burn up chart helps us in complementing the burn down chart well.
Burn down Vs Burn up chart
The decision to choose a chart is dependent on the overall project goal tracking. How the team is comfortable in tracking the progress of the project?
I have seen teams using both the charts. If your goal is to look at the remaining work to be done, then burn down chart is the best option. If you are looking to track the work completed vs the overall work, then burn up chart is the best option.
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