Citation

Burnham G, Roberts L. Science 2006; 314(5803): 1241; author reply 1241.

Affiliation

Johns Hopkins Bloomberg School of Public Health

Copyright

(Copyright © 2006, American Association for the Advancement of Science)

DOI

10.1126/science.314.5803.1241b

PMID

17124305

Abstract

 Letter (excerpt): John Bohannon's article "Iraqi death estimates called too high; methods faulted" (Science 314 (5798), 396. [DOI: 10.1126/science.314.5798.396]) contains several errors that require comment.

Bohannon fails to appreciate that cluster sampling is a random sampling method. Sampling for our study was designed to give all households an equal chance of being included. In this multistage cluster sampling, random selections were made at several levels ending with the "start" house being randomly chosen. From there, the house with the nearest front door was sampled until 39 consecutive houses were selected. This usually involved a chain of houses extending into two or three adjacent streets. Using two teams of two persons each, 40 houses could be surveyed in one day. Of our 47 clusters, 13 or 28% were rural, approximating the UN estimates for the rural population of Iraq.

Bohannon states that Gilbert Burnham did not know exactly how the Iraqi team conducted its survey. The text sent to Bohannon, which he fails to cite, said, "As far as selection of the start houses, in areas where there were residential streets that did not cross the main avenues in the area selected, these were included in the random street selection process, in an effort to reduce the selection bias that more busy streets would have." In no place does our Lancet paper say that the survey team avoided small back alleys. The methods section of the paper was modified with the suggestions of peer reviewers and the editorial staff. At no time did Burnham describe it to Bohannon as "oversimplified."

Those who work in conflict situations know that checkpoints often scrutinize written materials carried by those stopped, and their purpose may be questioned. Unique identifiers, such as neighborhoods, streets, and houses, would pose a risk not only to those in survey locations, but also to the survey teams. Protection of human subjects is always paramount in field research. Not including unique identifiers was specified in the approval the study received from the Johns Hopkins Bloomberg School of Public Health Committee on Human Research. At no time did the teams "destroy" details, as Bohannon contends. Not recording unique identifiers does not compromise the validity of our results.

Concerning mortality estimates, Michael Spagat may be content, as Bohannon claims, with mortality data collected barely 1 year into an escalating 3.5-year war. Others might not find these so helpful.

A response by Bohannon follows this letter.

Language: en