This only applies if you have to make a hire/skip decision immediately after each interview and can't go back later. (The formulation I usually see is a princes

This only applies if you have to make a hire/skip decision immediately after each interview and can't go back later. (The formulation I usually see is a princess choosing a suitor — for pride/face reasons, she can't pass on a suitor and then go back if it turns out he was the best of the bunch.) That's not typically how job interviews work, though. I think the magic number is 1/e of the applicant pool (e = Napier's constant, 2.7...)