The report's authors derive this figure by estimating how many Iraqis died in a 14-month period before the U.S. invasion, conducting surveys on how many died in a similar period after the invasion began (more on those surveys later), and subtracting the difference. That difference—the number of "extra" deaths in the post-invasion period—signifies the war's toll. That number is 98,000. But read the passage that cites the calculation more fully:
We estimate there were 98,000 extra deaths (95% CI 8000-194 000) during the post-war period.
Readers who are accustomed to perusing statistical documents know what the set of numbers in the parentheses means. For the other 99.9 percent of you, I'll spell it out in plain English—which, disturbingly, the study never does. It means that the authors are 95 percent confident that the war-caused deaths totaled some number between 8,000 and 194,000. (The number cited in plain language—98,000—is roughly at the halfway point in this absurdly vast range.)
This isn't an estimate. It's a dart board.
It just gets better from there.