May 23, 2005

Lunatic numbers...

Shannon Love has a must-read post, Number Gut:

When I was in college, one of my professors used to complain that too many of his students had no "number gut."

A number gut is an intuitive feel for the possible magnitude of a particular number that describes a particular phenomenon. A good number gut tells you if the results of some calculation are at least in the ball park. People develop number guts through experience with particular phenomena but they also develop it just by doing a lot math by hand. When you do math by hand, you have to do more physical writing to deal with very large numbers so you develop a kind of visceral sense of scale. The coming of calculators, however, destroyed this physical relationship, leading many budding scientists to make gross errors of magnitude without realizing it.

The lack of a number gut destroys any sense of context for numbers that describe a phenomenon, leading people to casually accept as valid statements that a little double-checking would show to be just plain silly.

For example, there was news story published back in the late 80s that reported that the state of New Jersey produced 50 billion used tires every year which caused a huge environmental problem. The story got widely disseminated before somebody pointed out that since New Jersey had a population on only around 8 million, 50 billion tires a year came out to 6,250 tires per capita per year. The story got play because the editors had no intuitive feel for the significance of 4 orders of magnitude difference between the size of the population and the tire consumption.

Which brings me to the subject of the
Lancet Iraqi Mortality Survey (LIMS) [free reg].....

I won't spoil the suspense by telling you what she says about the LIMS. It's assorts well with the New Jersey tire story. Go read...

(Thanks to Brian Tieman)

Posted by John Weidner at May 23, 2005 4:48 PM
Weblog by John Weidner