- in mathematical ability
- among schoolchildren
- on a standardized test
and generalizes them to:
- many different types of abilities
- among the Y Combinator applicant pool
- on the Y Combinator application process
Not only that, but by its end, the article is postulating a model in which literally one in a million people have sufficient aptitude to be accepted by Y Combinator - whether they're interested in it or not!
Even if you grant the author all of those assumptions, plus the risk aversion thing, you're only down to 13% women, three times what TechCrunch says Y Combinator actually accepts. I guess you could add another independent 99.9th percentile ability requirement, but then you're talking about one in a billion people being Y Combinator worthy. Or you could try to find a different, more tilted risk aversion statistic -- but at that point I think we'd be cherry-picking citations to fit a conclusion.
So, sure, if you accept a whole raft of dubious assumptions, you can explain the 4% acceptance rate by aptitude alone. But enough dubious assumptions can explain almost anything.