Gerd Gigerenzer's Calculated Risks is a good tool to fix numerical illiteracy. He explains that people are generally not good at thinking in terms of percentages but can figure out their odds better if given a base rate figure.One of the most important topics touched on in the book is the issue of false positives that can occur in medical test results. (Usually newspapers do not make any mention of false positives when they talk about disease-testing. My speculation is that it is not an issue most journalists are aware of or know how to present in a comprehensive fashion.)
Given that no test is ever 100% accurate, there will always be a chance that those who are disease-free will receive results that are positive.
The book describes the havoc this kind of misunderstandings can cause as people who receive a false positive result, even without the Aids virus, end up killing themselves or carrying out risky behaviour because they think they have the death sentence upon them.
Numbers can kill sometimes, I guess.
