> who wanted to go to KTH
Here's your selection bias. Self-selection is also selection.
Here's your selection bias. Self-selection is also selection.
You can look up the admission statistics yourself: it's very easy to get in to KTH. Maybe there are some programs that are more competitive than others.
When I finished high school, the admission criteria for example Electrical Engineering was roughly "you need a non-failing grade in all high school courses". How is that "elite"? Compare with medical school where it used to be "you need the best grade in every single course otherwise you're not getting in". Or the Opera school where there's an admission test in front of an audience.
I can guarantee that MIT is more difficult to get into than KTH.
It's true that looking at people admitted to elite medical schools would introduce even bigger bias, but it does not mean that the sample you chose is representative.
In this context it does not matter how elite KTH is. It only matters whether KTH students on average are materially different from general population.