Statistically questionable, but much better than most non-mathematical publications involving statistics. The problem is: every use of statistics outside of pure mathematics is questionable. Even in experimental physics, where perfect distributions are assumed, when an experimental setup may well lead to a bias. That's the major point the paper raises. Given the standards, I don't doubt for a second that this paper was rightfully published. If it wasn't, the question is: how many other papers weren't? I'd argue more than half of those employing statistics.