> The validity of IQ as a predictor of job performance is above zero for all work studied to date, but varies with the type of job and across different studies, ranging from 0.2 to 0.6

Best know doesn't mean good. Any occupation also fails:

> for minimally-skilled activities, athletic strength (manual strength, speed, stamina, and coordination) are more likely to influence performance.

https://en.m.wikipedia.org/wiki/Intelligence_quotient

Also, that's a predictor for "any" job. You can do better if you know exactly what job you're interested in. Do a sample of work that's very close to the real one and you'll have a better prediction.