Or you could quit debating about sampling systems, generalities and specificalities and just assume that all people are incompetent until proven otherwise. Chose who you'll work or travel with on a case by case basis. Sounds pretty harsh doesn't it?

I tend to find that men and women, children and old people, geniuses and morons all tend to have places where they are strong and where they are weak. In the military, in school and in my personal life, I've found most people are brilliant in some respects and thicker then a whale omelet in other ways. That's the problem with sexism, racism, and all those other -ism. They paste a wide variable population with arbitary and subjective narrow categories. Once people do that suddenly they're able to say "oh, I know you, you're a..." people meet before they meet.