I was honest. I went through a basic DFSS training , but have worked on a DFSS project. This was just not in my skill set. we talked about the steps in a DFSS project and the steps in a traditional SS project, so know DMAIC and be able to talk about that. We talked about different tools to use for root cause analysis. steps in an FMEA and when you would do it. (again, don't talk about stuff that you don't know)