Comment by sethammons

The rule of thumb I subscribed to: have the interviewer(s) do the interview. Give the candidate 3x time to do it that the in-house people took. Or, framed in reverse, if you want the assignment to take and n minutes or hours, give yourself n/3 to complete it, and however far you get is the bar for the assignment. Interviewees are stressed, maybe outside their domain, and other things. Make something that they can show you their value. The harder and correct thing to do is to find how they can help your org. It is easy to find what they don't know or to play stump the idiot.