 Nota day passes without some anti smoking autocrat trumpeting a piece of 'science'claiming, in essence, that we all die of smoking. Once again, on January 31'st,2007, the compressor horn was blown. In the ”American Journal of Public Health”no less than seven grant junkies published a 'study' claiming that 'passivesmoke' increases risk of lung cancer by 200 %. Here is the abstract. You need not pay for the study, let aloneread it. I'll explain the principles behind the study in a few brief sentences. First, we note that the 'study' is a meta-analysis. That meansit is just a rehash of some old 'studies'. Second we note that 20 'studies',from all over the world were 'selected'. That's all we need to know.
The 20 'studies' were, of course, cherrypicked. By virtue of the underlying studies being statistical, we understandthat some studies will randomly fluke up higher risks than other studies. Thereare at least 100 'studies' to pick from, so plucking the ones that 'prove' thedesired point is straightforward.
It's more or less like rolling dice. If youneed six'es, just roll enough times, and you'll get all the six'es you need.
Having selected the desired studies, therehashing is simple arithmetic. All the statistical analysis is a big circus toimpress the audience. What the study proves is that data mining can beused to conjure something out of nothing.
The study is a replay of one of the oldeststatistical tricks in the bag. I'll quote from a little book titled ”How To LieWith Statistics”, by Darell Huff, published 1954. From the opening sentence ofchapter 3, we have:
"What you shoulddo when told the results of a survey, a statistician once advised, is ask”How many juries did you poll before you found this one"”
A metaanalysis is simply another way ofplaying that trick.
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