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Thread: Statistics and Fibs, and how to tell the difference

  1. #1
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    Lightbulb Statistics and Fibs, and how to tell the difference

    Statistical tricks make you think stupid things. Don't fall for them.


    https://phys.org/news/2018-11-news-d...atistical.html

    Numbers in the news? Make sure you don't fall for these 3 statistical tricks

    November 1, 2018 by Liberty Vittert, The Conversation

    [example from text] - One of the most depressing headlines I ever read was "Eight-year study finds heavy French fry eaters have 'double' the chance of death." "Ugh," I said out loud, sipping my glass of red wine with a big ole basket of perfectly golden fries in front of me. Really?

    Well, yes, it's true according to a peer-reviewed study published in the American Journal of Clinical Nutrition. Eating french fries does double your risk of death. But, how many french fries, and moreover, what was my original risk of death?

    The study says that if you eat fried potatoes three times per week or more, you will double your risk of death. So let's take an average person in this study: a 60-year-old man. What is his risk of death, regardless of how many french fries he eats? One percent. That means that if you line up 100 60-year-old men, at least one of them will die in the next year simply because he is a 60-year-old man.

    Now, if all 100 of those men eat fried potatoes at least three times per week for their whole lives, yes, their risk of death doubles. But what is 1 percent doubled? Two percent. So instead of one of those 100 men dying over the course of the year, two of them will. And they get to eat fried potatoes three times a week or more for their entire lives sounds like a risk I'm willing to take.

    This is a statistical concept called relative risk. If the chance of getting some disease is 1 in a billion, even if you quadruple your risk of coming down with it, your risk is still only 4 in a billion. It ain't gonna happen.

    So next time you see an increase or decrease in risk, the first question you should ask is "an increase or decrease in risk from what original risk."
    There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.
    Mark Twain, Life on the Mississippi (1883)

  2. #2
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    Even "double the chance of death" is little dubious as the average "chance of death" is 100% !

    The BBC (radio) alternates between hyping up stories like this and getting someone to explain the concept of relative risk (often David Spiegelhalter, who is a Professor of the Public Understanding of Risk so should know what he is talking about).

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