Why are we working on this project, rather than others we could be doing?
How does this project relate to key objectives or initiatives of the organization?
What specifically are we trying to accomplish with this project? How will you measure success?
Can you show me a map of the process in question?
Were these CTQs validated by customers? If not, how were they validated?
Did you evaluate the measurement system? How? Where's the data?
What data do you have to corroborate that conclusion?
Did you plot the data? May I see the graph?
What hypothesis do you have about the process that would explain these data?
What other options for improvement did you consider? Why were they not selected? ...