I was amused when recently reading an article from the BBC, in which the author reported (in a horrified tone) about the health risks of Vitamin E. Did you know that taking a Vitamin E supplement means that your chances of getting a hemorrhagic stroke in the brain... just increased? By 22%?
That's quite a bit. That's a quarter of One Hundred Percent. That's got to be Statistically Significant. Well, I guess that means that none of us will be taking Vitamin E pills any time soon. Or should it?
What if we dig a little deeper into the story? Well, it turns out that of all the people they were following in this vitally important study, one extra person out of 1,250 persons ended up with a brain stroke.
One out of 1,250? Boy, that suddenly doesn't sound significant anymore, does it? That tiny fraction is certainly going to be less than the 22% scare figure that led the story. A quick mathematical calculation (in my head, of course) comes out as 0.08%. Couldn't that be attributed to mere chance? Hmmm.... This sounds like a classic case of making a news story out of a pig's ear. (Perhaps I mixed a metaphor there)
Here's a simple example of how easily statistics can be manipulated. Pretend that the city of Peoria is made up of 9999 persons. Two of you happen to have blonde hair, and the other 9997 Peoria dwellers (Peorians?) have brown hair. Then, you have a child who turns out blonde, just like you! There are now three people who have blonde hair out of the whole city of 10,000. Still not very many blondes, right? Only one more out of ten thousand, which any rational person would find impossible to pick out of a downtown crowd. However, statistically speaking, the number of blondes in Peoria just increased from 2 to 3, or an increase of 50%! Your chance of being born blonde in Peoria just increased by 50%! Call in the Journal Star, we're gonna have a press conference!
So what does it mean if one's risk of stroke increases by a large number when the actual number of strokes increase by so few? Using the example above, it means that the number was already tiny to begin with, and hasn't increased by much. The researchers, however, who spent valuable time and resources on this rather useless project, have to justify their use of valuable time and resources, and... VOILA! A news story that looks scary but isn't. It's highly unfortunate for the poor fellow who suffered the stroke, naturally, but statistically meaningless.
So many of these "increase your risk" news stories are based on faulty statistics like this. Don't be suckered. Look carefully through a story first, and make sure that the number of actual events are enough to worry you.
Unless otherwise attributed, all content is written by Kyle Johnson, DC, of Johnson Family Chiropractic of Peoria.
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