Or the journal editor, you definitely should. This is the kind of thing that can easily get cited in future work on the matter.

I sent an email to [email protected]. If they reply, I will post their response here.

Subject: elementary math error in journal article

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3615184/ was linked to and discussed today from Hacker News (a popular discussion board for software engineers) here https://news.ycombinator.com/item?id=22307445.

In the ensuing discussion a poster noticed that the journal article contains an elementary math error:

"if schizophrenia occurs at a rate of 0.72% in the population (McGrath et al., 2008) and congenital blindness occurs at an estimated rate of 0.03% in people born in the 1970s and 1980s (based on Robinson et al., 1987), then the joint probability of a person having both conditions, if the two are independent, would be 0.02% or 2 out of every 10,000."

0.72% * 0.03% is actually .0002% or 2 out of every 1,000,000.

Despite the article being several years old, I thought you might want to know.

-harryh

Great job; we need more good citizens like you!

I was unaware that they do at least have the implied 620 figure for the entire US correct, so there is hope that this is just a localised typo.

I can't get over how stunningly-similar this is to the infamous Verizonmath!

Well it's been a day and, sadly, I've received no response. The error also still appears on the publication's own website:

https://www.frontiersin.org/articles/10.3389/fpsyg.2013.0015...

Thank you for your effort. For someone who is in academia and a firm believer in the advancement of knowledge via peer-review, these things matter. Cheers!

it is probably not a math mistake since, when they applied the probability the 620 people is correct. Might be a typesetting (formatting) mistake. The 0.0002 is already a percent, but someone overlooked that and turned it again into percent.

Still it should definitely be corrected as the 2 out of 10,000 is a value that sticks in the mind.

I once helped setting an article in tex (originally written in word) and made the mistake of not noticing that rich text 10^20 got converted to 1020 in plain text. We only noticed post print but nobody else seem to have stumbled on it even though it was at the core of the articles thesis.

They also used the 2 in 10,000 figure when picking out the comparison syndromes. I believe Retts is ~1 in 10,000. It's definitely not 1 in a million.

My guess is the editor somehow messed up the per thousand sign ‱

https://en.wikipedia.org/wiki/Basis_point

edit: My bad. Correct character, incorrect description. It is indeed "ten thousand".

Somewhat ironically, I think you're off by one character here.

Unicode U+2031 ‱ is actually the per ten thousand sign (check its character name).

Unicode U+2030 ‰ is the per thousand (or "per mille") sign.

The one thing worse than off-by-one errors are off-by-zero errors.

Weirdly, as ChrisRR points out, they get the total number of predicted blind + scizophrenic people in the US correct. So it almost looks like more of a typo than a math error.

But still.

It makes sense, because as a scientist you often only write it as e.g. 0.2% for the article, but 0.002 in your actual calculation.

Percentage calculations being off by 2 zeros I would say is one of the most common mistakes I saw in, e.g. statistics exams.