This refereed medical journal article, like many others, made the same mistake as my undergraduate logic students, moving the negation across the quantifier without changing the quantifier. I cannot recall ever seeing a medical journal article prove a negation and not make this mistake when stating its conclusions.

That would be interesting if true. I recommend finding another one, since you sya they're so plentiful. And I also recommend reading it carefully, as the study you chose to make an example of is not the study you were looking for. (If you don't want to change the exemplar study, it may also be of interest what is your prior for "PhilGoetz is right where all of LessWrong is wrong')

The different but related question of the proportion of people (especially scientists, regulators, and legislators) misinterpreting such studies might also be worth looking into. It wouldn't surprise me if people who know better make the same mistake as your logic students, possibly in their subconscious probability sum.