"Hard Interviews, Happy Workers". This note near the end assumes correlation shows causation, which it does not. You could also argue that more workers want to

"Hard Interviews, Happy Workers". This note near the end assumes correlation shows causation, which it does not. You could also argue that more workers want to work in certain jobs, creating more competition and leading the company to make interviews harder. The workers in those jobs may be happier, but not because the interviews were harder.