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In my opinion, based on my and my friends' experience, being good at programming competitions clearly makes you very good at interviewing. I don't think that b

by xyzzyz 9y ago

In my opinion, based on my and my friends' experience, being good at programming competitions clearly makes you very good at interviewing. I don't think that being good at contests makes you bad at the job, though. Consider the following scenario: assume that skill of being good at contests is completely orthogonal to being good at the job (so the real correlation coefficient is 0, instead of negative, observed by Norvig). Then, since it's easier to to get hired if you're good at contests, the observed correlation coefficient inside a single company will be negative, due to selection bias. Depending on the effect sizes, the selection bias might even make observed correlation coefficient negative even if it's positive in reality (which I think it is). For a more intuitive explanation, consider a used car market buyer who has preference for black cars (this corresponds to algorithm-based interview process of companies like Google or Facebook). Even though the color of the car should have no correlation with its quality, the black cars owned by that buyer will more likely be worse quality than non-black ones.

thaumasiotes 9y ago
> Depending on the effect sizes, the selection bias might even make observed correlation coefficient negative even if it's positive in reality (which I think it is). This is well known in SAT scores. SAT math and verbal scores have a very strong positive correlation in reality; inside almost all colleges they are negatively correlated, because colleges impose threshold effects below and above. (That is, colleges admit students in a narrow band of SAT scores, rather than admitting students who are above a minimum threshold.) You can stylize that into the idea that total SAT score is constant for the students in any given college, which easily explains why component scores would be negatively correlated within colleges.

by xyzzyz 9y ago

thaumasiotes 9y ago

> Depending on the effect sizes, the selection bias might even make observed correlation coefficient negative even if it's positive in reality (which I think it is). This is well known in SAT scores. SAT math and verbal scores have a very strong positive correlation in reality; inside almost all colleges they are negatively correlated, because colleges impose threshold effects below and above. (That is, colleges admit students in a narrow band of SAT scores, rather than admitting students who are above a minimum threshold.) You can stylize that into the idea that total SAT score is constant for the students in any given college, which easily explains why component scores would be negatively correlated within colleges.