Tuesday, October 04, 2005

Numerazzberry

A great big numeracy razzberry goes to South Carolina's health department.

On its minority health disparities page it has this list:

Did You Know...

  • Racial and ethnic minority infants in South Carolina are more than twice as likely to die before their first birthday than white babies.
  • In the year 2000, African Americans were over nine times more likely to be reported as having HIV/AIDS than were whites.
  • Although the incidence of female breast cancer in SC is higher for whites, minority women, in particular African American women, are nearly twice as likely to die of the disease.
Nice job of mixing unequal things to create a mishmash. As sara Cohen so ably notes in her book, Numbers in the Newsroom, when it comes to relative risk, more likely than and as likely as are not the same thing.

Think of as likely as as multiplication. If 20 percent of black babies die before their first birthday and 5 percent of whites (those are not the real numbers), then a black baby is four times as likely to die before its first birthday.

But that same baby is three times more likely. (5 plus 15 --or three 5's)

The problem is that people tend to think more likely means as likely. It does no one any good to mix the terms, as journalists sometimes do. Agencies like the state Department of Health and Control -- as well as journalists -- can do better.

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