Source: Crooked Timber
by Daniel Davies
November 1, 2004

As Chris said, with respect to the Lancet study on excess Iraqi deaths, “I can predict with certainty that there will be numerous posts on weblogs supporting the war attacking the study”. Score several Cassandra points for Chris, they weren’t slow in coming. You can have the know-nothing rightwing flack variety or the handwringing liberal variety. And to be honest, the standard of critique is enough to make you weep.

Taking the complaints that seem to have been raised about this study:

“That is, a one in twenty chance that the effect simply does not exist” (from Tech Central Station). The author of the TCS piece appears to believe that because the Lancet study published a 95% confidence interval, there is a 5% chance that there was no effect. The problem with this critique is that it is not true.

“a relative risk ratio of anything less than three is regarded as statistically insignificant”. This is also from TCS, and also, simply, not true. Interesting to note that TCS appear to have upped the ante on this piece of bogus epidemiology; historically when they have been talking about passive smoking, the threshold for relative risk ratios has been two. Which is also bollocks. The TCS author appears to have a very shaky grasp of the statistical concepts he is using.

“This isn’t an estimate. It’s a dart board”. The critique here, from Slate, is that the 95% confidence interval for the estimate of excess deaths (8,000 to 200,000) is so wide that it’s meaningless. It’s wrong. Although there are a lot of numbers between 8,000 and 200,000, one of the ones that isn’t is a little number called zero. That’s quite startling. One might have hoped that there was at least some chance that the Iraq war might have had a positive effect on death rates in Iraq. But the confidence interval from this piece of work suggests that there would be only a 2.5% chance of getting this sort of result from the sample if the true effect of the invasion had been favourable. A curious basis for a humanitarian intervention; “we must invade, because Saddam is killing thousands of his citizens every year, and we will kill only 8,000 more”.

The estimate of prewar mortality is too low. The idea here is that the sample chosen for the survey had a mortality rate of about 5 per 1000 in the two years before the invasion. And, because the death rate for the period 1985-90 was 6.8 per 1000 according to UN figures, this in some way suggests that the estimates are at fault.

This critique is more interesting, but hardly devastating. For one thing, the contention that the Iraqi death rate did not fall from 6.8 to around 5 during the 1990s is based on “it must have done” rather than on hard numbers. Since the 6.8 number includes (as far as I can tell) atrocities committed by Saddam du