Friday the 13th

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Friday 13th. What could possibly go wrong today?

Well, according to people who suffer from Friggatriskaidekaphobia – the fear of Friday 13th – rather a lot. But is there any rationale for a fear of Friday 13th?

The scientific evidence is patchy. One study published in the British Medical Journal – ‘Is Friday the 13th bad for your health‘ – apparently found a 52% increase in hospital admissions from road accidents on Fridays that fell on the 13th of the month, compared with other Fridays.  However, one of the authors, Robert Luben, was subsequently quoted as saying:

It’s quite amusing and written with tongue firmly in cheek. It was written for the Christmas edition of the British Medical Journal, which usually carries fun or spoof articles.

I guess the authors looked at several possible statistics and reported the one that, by chance, fitted the hypothesis of Friday the 13th being unlucky. We’ve discussed this issue before: if you look at enough different phenomena where there is nothing of interest, some of them will look like there is something interesting happening just by chance. Statistics as a subject can be – and often is – badly misused this way,

Not everyone seemed to see it as a joke though. A follow-up study in the American Journal of Psychiatry titled ‘Traffic Deaths and Superstition on Friday the 13th‘  found a higher accident rate for women, but not men, on Fridays falling on the 13th of the month. This was subsequently contested by another group of researchers who published an article in the Journal BMC Public Health magazine titled ‘Females do not have more injury road accidents on Friday the 13th‘. Who to believe?

So, it’s a mixed bag. Moreover, as reported in Wikipedia – which gives an interesting history of the origins of the superstitions associated with Friday 13th – road accidents, in the Netherlands at least, are less frequent on Friday 13th, arguably because people take more care than usual. But even there I’d be cautious about the results without having a detailed look at the way the statistical analysis was carried out.

And anyway, Tuesday 8th is the new Friday 13th. You’ve been warned.


Footnote: I’m writing this on Thursday 12th, blissfully unaware of whatever horrors this particular Friday 13th will bring.

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