At the risk of repeating what I commented below, I like to say the same thing differently, which seems to resonate with students in the class:

Interviewing, by definition, is not a standardized test with a standardized evaluation. On the spectrum of human interactions, it's closer to a date, than it's to a test.

In doing interview coaching/training for a living (http://interviewkickstart.com), I see this every day. It's frustrating to a certain degree, but also very powerful once understood.

Also see my Quora answer here: https://www.quora.com/What-are-the-biggest-mistakes-that-eng...