You need to read the whole thread for context. The original post claims education quality in Sweden deteriorated. username90 argues it didn't, using unchanged KTH test results as support. JorgeGT says KTH is an elite institution so there is a selection bias. You disagree, saying that KTH is not an elite institution. I'm saying the selection bias is still present because KTH students are not a representative sample.

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.