...Many people confuse the statement "almost all terrorists are Moslems" with "almost all Moslems are terrorists." Assume that the first statement is true, that 99 percent of terrorists are Moslems. This would mean that only about .001 percent of Moslems are terrorists, since there are more than 1 billion and only, say, ten thousand terrorists, one in a hundred thousand. So the logical mistake makes you (unconsciously) overestimate the odds of a randomly drawn individual Moslem person (between the age of, say, fifteen and fifty) being a terrorist by close to fifty thousand times!

The reader might see in this round-trip fallacy the unfairness of stereotypes - minorities in urban areas in the United States have suffered from the same confusion: even if most criminals come from their ethnic subgroup, most of their ethnic subgroup are not criminals, but they still suffer from discrimination by people who should know better.

"I never meant to say that the Conservatives are generally stupid. I meant to say that stupid people are generally Conservative," John Stuart Mill once complained...

(Excerpt from Nassim N. Taleb "The Black Swan". For more on presidential IQs: http://www.lovenstein.org/report/)