By definition, 50% of the population has an IQ between 90 and 110. While it is plausible that there is a disproportionately low number of HN commenters in the bottom quartile for IQ, I believe that the majority, if not the plurality, of HN commenters will fall in the range of (90, 110).
35% of the US population over 25 has a Bachelor's degree. Assuming that, say, the top 40% in IQ of the total population is capable of completing such a degree and that HN commenters are a randomly distributed subset of that population, that would leave a lower bound for IQ of 104 and a median IQ of 113.
The reality is that IQ is unlikely to be the limiting factor when it comes to whether or not it is possible to retrain large portions of the working population.
