Iraq Poll: Note on Methodology
March 17, 2008 — -- This survey was conducted for ABC News, the BBC, ARD and NHK by D3 Systems of Vienna, Va., and KA Research Ltd. of Istanbul, Turkey. Interviews were conducted in person, in Arabic or Kurdish, among a random national sample of 2,228 Iraqis aged 18 and up from Feb. 12 to 20, 2008.
Four-hundred-sixty-one sampling points were distributed proportionate to population size in each of Iraq's 18 provinces, then in all 102 districts within the provinces, then by simple random sampling among Iraq's nearly 11,000 villages or neighborhoods, with urban/rural stratification at each stage.
Maps or grids were used to select random starting points within each sampling point, with household selection by random route/random interval and within-household selection by the "next-birthday" method. An average of five interviews were conducted per sampling point. Seven of the 461 sampling points were inaccessible for security reasons and were substituted with randomly selected replacements.
Interviews were conducted by 116 trained Iraqi interviewers with 31 supervisors. Fifty-seven percent of interviews were supervised or reviewed by supervisors – 34 percent by direct observation, 7 percent by revisits and 16 percent by phone. All questionnaires were subject to further quality-control checks.
In addition to the national sample, oversamples were drawn in Anbar province, Sadr City, Basra city, Kirkuk city and Mosul to allow for more reliable analysis in those areas. Population data came from 2005 estimates by the Iraq Ministry of Planning. The sample was weighted by sex, age, education, urban/rural status and population of province.
The survey had a contact rate of 92 percent and a cooperation rate of 65 percent for a net response rate of 60 percent. Including an estimated design effect of 1.52, the results have a margin of sampling error of 2.5 percentage points at the 95 percent confidence level.
SUNNI/SHIITE – Given the attitudinal differences between Shiite and Sunni Arabs in Iraq, there's interest in the relative sizes of these two groups. We find no official Iraqi estimate of the country's Sunni vs. Shiite Arab populations and no authoritative source of empirical data on the subject.
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