Actually, it's worse than that. The job itself can be a noisy signal,
since people often mold a job around their skills. If I find an applicant
who's very good in one area but not great in another, I think about how I
can adjust the job requirements to them. And often I don't even have a
perfect idea of the job I need done. (Mind you, the solution is often to
hire people who seem *really* smart, regardless of their background, and
use them in what ever way works.)
I find I'm bothered by the claim that interviews are not predictive, though
I have heard that in many places. At a previous company, we gave a
take-home programming test to the applicants that looked interesting. At
least once I chose a programmer who had a less impressive test but better
people and verbal skills, because they would need to work in a team with
non-programmers. Some how I don't think IQ would have captured that
difference.