Apropos a discussion on the effects of the Bush tax cut at FactCheck.org and Begging to Differ, Chris Lawrence gives us a review of two often-confused measures of central tendency, the mean and the median.* It’s rather common practice for sides in a debate to pick the one that best fits their argument. The press typically doesn’t help matters by using the word “average,” usually understood to be a synonym for arithmetic mean, carelessly.
I agree with Chris that the median is almost always a more useful indicator, since the mean can be skewed by huge figures even in a large sample. This is especially true for income and similar economic variables, which are bounded at the bottom but not at the top. Even with something as large as the U.S. population, a handful of billionaires can skew the stats–whereas even the poorest of the poor have only a miniscule effect.
*Typically, he makes no mention of the mode, the nearly useless third measure.
