In July 1982, paleontologist Steven Jay Gould was diagnosed with cancer. Facing a median prognosis of only 8 months survival, he used his knowledge of statistics to prepare for the future. As he explains in The Median Isn’t the Message, if half of the patients died of this rare case of mesothelioma within 8 months, those who did not had much better survival. Evaluating his own chances of being in the “survivor” group as high, he planned for long term survival and opted out of the standard treatment. He died 20 years later, from an unrelated disease.

If not the median, then what is the message? Statistics put a disproportionate emphasis on the typical or average behavior, when what matters is sometimes in the extremes. This general blindness to the extremes is responsible for a dreadful lot of confusion in the bio-medical field. One of my all time favorite traps is the extreme value fallacy. Nothing better than an example will explain what it is about.

June babies and anorexia

If the perfect mistake was ever made, it definitely was in an article about anorexia published in 2001. A more accessible version of the story was...