People prefer precise percentages.

• Position: Statistics

Would you rather support research for a disease that affects 30,000 Americans a year or one that affects just .01% of the U.S. population? The numbers represent about the same amount of people, but how you answered explains the way in which you understand numerical information, suggests a psychology professor at Kansas State University, Manhattan.

"People are comfortable with simple frequencies and statistics," maintains Gary Brase. "Everybody can understand five, six, 10, 20, or even 100, and percentages like 30% or 40%. We have a really good sense of how much that is, but it's really large numbers that we don't have nailed down. If you say there were 20,000 people at a concert versus 30,000 people, we don't have a good sense of how much bigger that is exactly."

Brase conducted two studies. Individuals had to compare two statements using different numerical formats. Participants were asked which statement was clearer and which expressed a greater value. The research shows that people find percentages and simple frequencies, such as one-third or two-out-of-five, easiest to understand. However, they also perceived absolute frequencies-like 30,000,000 Americans, for instance--to be a greater number than a fraction or ratio, even when the numbers were equivalent.

Another study analyzed the responses to postcards asking recipients to show their support for cancer research. Each group...