The researchers saved the most dangerous location for last. On September 20, Dr. Lafta went to violence-racked Fallujah with the only interviewer willing to travel there. The researchers had done a haunting bit of calculus before the journey. Given that the chance was high of an interviewer's or researcher's getting killed there, the study would be better served by getting the other data first.
The Fallujah data were chilling: 53 deaths had taken place in the study's 30 households there since the invasion commenced, on March 19, 2003. In the other 32 neighborhoods combined, the researchers had counted 89 deaths. While 21 of the deaths elsewhere were attributable to violence, in Fallujah 52 of the 53 deaths were due to violence.
The number of deaths in Fallujah was so much higher than in other locations that the researchers excluded the data from their overall estimate as a statistical outlier. Because of that, Mr. Roberts says, chances are good that the actual number of deaths caused by the invasion and occupation is higher than 100,000.
Scientists say the size of the survey was adequate for extrapolation to the entire country. "That's a classical sample size," says Michael J. Toole, head of the Center for International Health at the Burnet Institute, an Australian research organization. Researchers typically conduct surveys in 30 neighborhoods, so the Iraq study's total of 33 strengthens its conclusions. "I just don't see any evidence of significant exaggeration," he says.
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