Monday, January 17, 2011

Journalists. Damn journalists, and statistics!

I don't know what made me click on this article about sunbed use today, but I was sorry I did.

The dire warnings about sunbeds causing skin cancer have gone unheeded, the article would have us believe. However, when you look closely you just realize that maths wasn't a favourite subject of the journalist writing (or cut and pasting) this pointless piece.

The article claims that a "study that recruited around 1000 members of Cross Health Society, found that out of 33% people aged between 21 and 29 who used sunbed, 3% were the regulars while no less than 27% would like to go for it again."

Let's look at those numbers, shall we.

Even if the entire survey was made up of only 21-29 year olds (it wasn't) then 3% of 33% of 1000 are regular users. That's 10 people.

Assuming a standard age distribution of survey participants, and assuming no-one under 21 was surveyed that would suggest about 7 people at best, probably less were discovered to be regular sunbed users. The article does not claim that anyone outside this age group were regular users.

So, 0.7% (or less) of people surveyed were regular users of sunbeds.

Or if you prefer, statistically speaking the number of regular users was insignificant. Practically speaking you can say that for all intents and purposes there is nothing to worry about with numbers like those. New Zealand has no problem use of sunbeds. Yet the article tries to make it read like an epidemic.

The article goes on to talk about sunburn rates from being out in the sun, but somehow uses those to make a claim about sunbed use?


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