A study which found that more than 650,000 Iraqi people have died since the US-led invasion was attacked yesterday by scientists in the UK, who claimed that the households interviewed tended to be located in violence-hit streets.
Sean Gourley and Professor Neil Johnson of the physics department at Oxford University and Professor Michael Spagat of the economics department of Royal Holloway, University of London, claimed the methodology of the study was fundamentally flawed by what they term "main street bias".
But the lead author of the study, which was published by the Lancet medical journal, said their criticism was "a misconception". Gilbert Burnham of the Johns Hopkins school of public health in Baltimore, said the methodology had not been published in full by the Lancet and that streets away from obvious conflict had been chosen.
Prof Spagat and colleagues levelled their criticism in email exchanges with Prof Burnham and colleagues which were mediated by Science magazine. They claimed the sampling methods used "will result in an over-estimation of the death toll in Iraq".
The Lancet researchers interviewed 40 households in 47 clusters randomly chosen across Iraq to reflect the spread of the population. The starting point for each cluster was the main street. Residential streets were then chosen which crossed the main street.
The critics argued that the Lancet paper does not indicate that the researchers moved far enough away from the main street. "The further away you get, the further you are from the convoys that roll down the streets and the car bombs and the general violence," said Sean Gourley. "By sampling only cross streets which are more accessible, you get an over-estimation of deaths."
But Prof Burnham said the researchers penetrated much further into residential areas than was clear from the Lancet paper.
The notion "that we avoided back alleys was totally untrue". He added that 28% of households were in rural areas - which matches the population spread.
Others had suggested that it was impossible for 40 households to be surveyed in one day - but in fact the researchers were split into two teams and conducted 20 household interviews each, he said. "Our point is that it is a big number, we set out to prove that we had the power to say the mortality rate has more than doubled."
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