Liberally Conservative

"Freedom is never more than one generation away from extinction. We didn't pass it to our children in the bloodstream. It must be fought for, protected, and handed on for them to do the same, or one day we will spend our sunset years telling our children and our children's children what it was once like in the United States where men were free....... ~Ronald Reagan~

Wednesday, October 18, 2006

How Not to Take A Statistical Sampling

In early days of college we are forced to take mandatory courses as Sociology and Psychology and I still remember discussing taking random samples of the statistical nature, discussing sampling size, sampling group and validity.
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One must wonder why a "group", associated with the Johns Hopkins Bloomberg School of Public Health, had so much trouble adding up numbers of casuality numbers in Iraq where they claim 655,000 Iraqis have died as a result of the war. the figure is at odds, with numbers from several sources.
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Instead of a margin of error of plus or minus 3% - 5% the margin is closer to 1200%. Stephen Moore, a political consultant with Gorton Moore International, knows of such matters. Mr. Moore trained Iraqi researchers for the International Republican Institute from 2003 to 2004 and conducted survey research for the Coalition Forces from 2005 to 2006.
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Here is what Mr. Moore explains about the methods employed by John Hopkins group:
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The group employed cluster sampling for in-person interviews, which is the methodology that I and most researchers use in developing countries. However, the key to the validity of cluster sampling is to use enough cluster points. In their 2006 report, "Mortality after the 2003 invasion of Iraq: a cross-sectional sample survey," the Johns Hopkins team says it used 47 cluster points for their sample of 1,849 interviews. This is astonishing: I wouldn't survey a junior high school, no less an entire country, using only 47 cluster points.
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For its 2004 survey of Iraq, the United Nations Development Program (UNDP) used 2,200 cluster points of 10 interviews each for a total sample of 21,688. A 2005 survey conducted by ABC News, Time magazine, the BBC, NHK and Der Spiegel used 135 cluster points with a sample size of 1,711 -- almost three times that of the Johns Hopkins team for 93% of the sample size.
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With so few cluster points, it is highly unlikely the Johns Hopkins survey is representative of the population in Iraq. However, there is a definitive method of establishing if it is. Recording the gender, age, education and other demographic characteristics of the respondents allows a researcher to compare his survey results to a known demographic instrument, such as a census.
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Dr. Les Roberts, one of the key authors in the Hopkins group said his team's surveyors did not ask demographic questions. In the 2006 Johns Hopkins study, nobody, according to Dr. Roberts, recorded demographic information for the living survey respondents. Without demographic information to assure a representative sample, there is no way anyone can prove -- or disprove -- that the Johns Hopkins estimate of Iraqi civilian deaths is accurate.
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We ask what other purpose the John Hopkins study serves, as it's released so close to an election? With numbers so blatantly out of the norm, we should believe this is one more "October Surprise" based on partisan fiction.
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Source: Wall Street Journal (Subscription)

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