Lisa rates potential boyfriends on two criteria, Looks and Personality, on a 0-50 scale each, for a potential combined score range of 0-100. She'll date someone only if their combined score is 50 or higher.
It's very likely that Looks and Personality will be negatively correlated among those who meet the cutoff, even if they're moderately correlated among the population as a whole.
My informal goto example to explain this to co-workers is:
If you look at multiple people's CVs, you expect the ones with more typos to be less impressive.
But if you restrict yourself only to people who worked at Google, you expect the guy who got hired despite lots of typos to be rather exceptional.
Similarly, Matt Levine wrote that you should expect hedge fund managers who look the least like hedge fund managers to do best.
I do the old two-score cutoff, for example
Lisa rates potential boyfriends on two criteria, Looks and Personality, on a 0-50 scale each, for a potential combined score range of 0-100. She'll date someone only if their combined score is 50 or higher.
It's very likely that Looks and Personality will be negatively correlated among those who meet the cutoff, even if they're moderately correlated among the population as a whole.
well done
Very informative, thank you. Also, "performance comes form general ability" - did you mean from?