# Mathematical Digest

### Short Summaries of Articles about Mathematics

in the Popular Press

"AAAS Statisticians Estimate Deaths from Conflict in Peru," edited by Coimbra Sirica. *Science*, 29 August 2003.

"Statistical model leaves Peru counting the cost of civil war," by Jonathan Knight. *Nature*, 4 September 2003.

During the summer of 2003 members of the human rights staff of the American Association for the Advancement of Science went to Peru to take part in the release to the public of a report "How Many Peruvians Died?---An Estimate of the Total Number of Victims of the Internal Armed Conflict, 1980-2000." The report, put together by scientists including Jana Asher, a statistical consultant for AAAS, concluded that 69,280 people were killed or "disappeared" during the 20-year conflict.

According to the *Nature* article, "Ball [the report's lead author] and his colleagues applied a statistical method developed in the late nineteenth century to count wild animals. It has since been used to adjust census estimates of hard-to-count groups such as the homeless." The method, called "Multi-systems estimation (MSE), relies on the existence of overlapping partial counts of a population, [and figures that] the chance of an individual appearing on two lists is equal to the product of their chances of appearing on each list seprately. Ball's team compared seven lists of dead and missing people compiled since 1980" and "factored in potential sources of bias."

*--- Annette Emerson*