Asking good questions in lab courses We are re-writing a bunch of our lab manuals for a first year circuits course.  We want to make a mix of focused questions ("what was the voltage across X?") and thought-provoking questions.  

At the moment, the "thought provoking" questions in the current lab manuals are all variations on "comment on the differences between your pre-lab and your experiment".  These invariably get students to just chime off a litany of "errors in the equipment" without really thinking it through.  What I would like to see the students doing is a thorough comparison and making a value judgment, and mentioning their observations.

I feel that the issue I'm having is that the focused questions are way too specific (just write down the number) but useful for learning certain things like how to take measurements.  Thus they are valid questions if not outstanding ones.  The thought provoking questions, though, are vague and don't get us what we're really looking for.  Can anyone suggest some in-between questions that give students a hint at what we are looking for without just asking them out right?
I can tell you how I've been seeing this handled at the K-12 level.  (I don't know if this is a good way to do it at that level or at the college level.)

A math problem is posed.  Then the narrator outlines how a fictitious student, e.g. Marisol, reasoned.  Often, this reasoning is flawed.  Then the student is asked to evaluate Marisol's reasoning.