I work in healthcare IT and many times have heard an “I’m just a nurse” dodge, and I respond in just this fashion — “Good! Then you have just the skills needed. In fact you don’t even have to diagnose the problem, just document what you did, what happened, and how that differs from what you expected.” It works pretty well.
"a) I do exactly this, b) expected this outcome, c) but got this instead"
Short and to the point, it's remarkable how much easier it makes things for everyone. I think I got it off usenet at some time.