We have up to several team members that does not work 100% on our team. You might argue that this is a bad idea in the first place, but lets assume we can't do anything about it. I have had a discussion with one of the other team members, and my argument is that the burndown chart is "lying" to us. Let me give you an example.
Lets say we have a sprint, lasting 2 weeks. We have 6 members, where 2 of them are only working 50%. If both of the part time members work 100% the first week, and 0% the second week, my argument is that after 1 week, the burndown will look alot better than the reality is. Scrum says that this is the time to add features to the sprint.
Ive seen an alternative way to do this, where you beforehand type in the days you are available, and then have a nonlinear ideal line. My first suggestion was to have placeholders to burn down even if you were not available, but that was shot down pretty quickly.
So I wonder; Should we do anything with the burndownchart? Is the chart even useful? Are there other good practices to overcome this hinderance?
We are currently using Urban Turtle