Friday, April 20, 2007

Very, Very Wide

Very thorough interview of Les Roberts on a (British?) news show. Highly recommended. Key part for my concern about confidence intervals comes in Roberts discussion of the 2004 study at around 3:50.

There was one place, the city of Falluja which had just been devasted by shelling and bombing. It was so far out of whack with all the other [clusters] that it just made our confidence intervals very, very wide.

Unfortunately, the interviewer quickly moves on to other issues. Compare that statement with Burnham's.

Now this is what the confidence intervals would look like. There is a 10% probability that it was less than 44,000 and only a 2.5% chance that it was less than 8,000. If we put Falluja into it, the top end of the confidence interval would be infinity. It really skewed things so badly that we decided that we should just leave it out and be conservative.

Seems fairly obvious to me that, if Falluja is included in Lancet I, the null hypothesis of no increase in mortality can not be rejected. But that's an empirical question. If the authors would release the data for Lancet I, we can figure this out.


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