You're missing the quality they're actually testing for: ability to study and dedicate yourself to a task. Or in other words work ethic. The algorithms don't matter but the fact that you can spend months learning them is an important skill. Intelligence is less important for success than work ethic which is why work ethic is tested for so much. Specifically, work ethic and ability to learn in a related domain as, for example, literature study skills may not transfer.
>If there was a perfect correlation between pre and post entrance test performance there wouldn't be PIPs, performance based layoffs etc.
Nothing is perfect, saying it's useless because it's not perfect is a silly argument.
>If there was a perfect correlation between pre and post entrance test performance there wouldn't be PIPs, performance based layoffs etc.
Nothing is perfect, saying it's useless because it's not perfect is a silly argument.