Good catch. Additionally, one of the authors on this is just a student at UWisc, and the other author is also not a professional researcher but instead an author of popular books.

This is not an ad-hominum, but does put into question the statistical training backgrounds of both of these authors to accurate assess the data.

> and the other author is also not a professional researcher but instead an author of popular books.

This makes the awkward wording even more confusing. I don't understand how a professional author who appears to speak English very well would write so poorly and not follow up with edits.

> but does put into question the statistical training backgrounds

This is true of virtually all university research. Statistics is far more nuanced than what a semester course can teach you. And the incentives to publish can cause bad actors to use poorly defined surveys or p hack or whatever.