Earlier quoted context omitted.
The solution to the problem in question is about 9 lines of very simple code. In a 45 minute interview, that is 5 minutes per line available. It's about 1 character every 40 seconds. I think anyone can get flustered and mess up. It's possible for someone, on a bad day, lack of sleep, hung over, experiencing an anxiety attack to mess this up, but it's really really a stretch. This is a VERY EASY task, and if someone h…
I completely agree that this is a very simple problem; I'm not at all arguing that it isn't. What I am arguing is that this doesn't make it super-unlikely that an otherwise competent person screws it up . If it's really a 1-in-10,000 event, isn't it rather surprising that we've got someone right here in this thread to whom it happened? Someone, moreover, not just barely competent but able to do well with a demanding…
Lets say we interview 100 (N) people for a role. (100 is a lot but pick a number yourself and follow along)
The probability that a random interviewee is a top programmer is lets say 1/50 (T). So in our pool of 100 we have on average 2. Give everyone this problem, and if they get it right they move to round 2 which is 4 more interviews. Lets say 20 (P) people pass to round #2.
We are paying for a total of 100 + 80 = 180 interviews (N + 4P). To give everyone who failed the first round another try would require another 80 (N - P) interviews. So for almost 50% more cost (N-P)/(N + 4P) we gain (T * N * 5%) = 0.1 additional top programmer making it to round 2 on average. Just interviewing another 80 people (same cost) would get us (T * 80 * 95%) == 1.52 additional top programmers to round #2 on average. There's basically no reasonable % you can pick for how often people screw up where it makes sense to do anything but just ignore the possibility.