In principal they are used for the same reason, to show the progress of the iteration.
But there are some small and important differences.
So lets look at this difference.
Before we go into more details, you have to know what a burn up and a burn down chart is. Check this link to Wikepedia, it should explain it very well: Wikipedia
In the ideal world, which never appears in an agile surrounding you can use a burn up chart, which shows the progress for each iteration over the time, until you reach the end of the project.
So a very simple example would be this:
Now think about, what happens if we get new requirements during the project?
Yes, in the agile world we add them and within one of the next iterations they will be done.
So as you can see, the line would go up, before in one of the next steps it would go done again, as soon as we would have finished work again.
As it is not that unusual, that we get new features, that we will delete some, the line could look very tricky. Think about a line for one iteration, where we would get some new features, while we just finished the work on some features. Let's stop here, for the exam, we will not face these complicated cases.
So let's switch to the burn up charts
Here an example, very simple again, of a burn up chart.
The top line shows the amount of features, or the complete scope, this line to reach is our goal.
So, what can happen to our project? We get more work or we will delete work. (Or with other words, the scope changes) This should be shown in the chart as well. But in the burn down chart, the line gives than no longer an easy overview.
The next picture shows how it looks, if we have to add new work to the burn up chart.
So here you can see in one diagram two tendencies: the progress of work completed (the line goes up) and secondly, all changes to our scope.
Good luck on the exam.
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