Bad Maths

While I'm on the subject of Bad Science, Ben Goldacre's entertaining dissection of the alternative medicine industry and the bad practices of the pharamcuticals industry...

The trouble (or maybe the advantage) of reading this kind of stuff is that you can't stop noticing examples all around you when you have read it.For example there is a report that I heard on TV at least half a dozen times yesterday which says, in various paraphrases, that "men are up to 70% more likely to die of cancer than women."

The suggestion is that this is a) terrible and b) due to men's lifestyles.The trouble is that the bare statistic is entirely meaningless unless they give a lot more information with it. We need to know what they mean by 70% more likely. We need to know if they are talking about men who have cancer being more likely to die than women who have cancer or do they mean men and women from the whole population.

On its own the bald statement is indecipherable. For example, if 1 woman in 1000 dies of cancer then this figure means that slightly less than two men in a thousand do. Whereas if 100 women in 1000 die of cancer then 170 men do. Rather more significant.If we are talking about the number of cancer patients who die (rather than the number of people who die of cancer), the maths gets more complicated because we would need to know the incidence of cancer in male and female populations as well as the actual relative sizes of those populations before the statistic becomes meaningful.This imprecise use of mathematical language isn't hard to understand - it arises because journalists need a short quick way of saying things without giving long explanations and most of them probably don't understand that their statistics are, as presented, completely meaningless.

And that's before we look at the intuitive leap that says it's down to lifestyle differences.

I must look up the actual research paper and see what it really says.