Thread:Standard deviation =! average distance from mean (1)

Hi folks, I'm new to WikiEducator, came across this page by happenstance. I noticed that in a couple of places, the article defined the standard deviation as "the average distance from the mean". This is a common belief and intuitively "sounds true" but unfortunately it's simply not the case. The standard deviation is close to the average distance from the mean (i.e. the mean absolute deviation), but will in almost all cases be larger than the mean absolute deviation. This can be easily verified (try it). Taking the Falcon example in the article, for instance, the standard deviation is 4, but the mean (absolute) deviation is 3. Incidentally, the difference isn't just due to the use N-1 in the variance/SD formula. This article discusses the difference between the SD and mean deviation: http://www.tandfonline.com/doi/abs/10.1111/j.1467-8527.2005.00304.x I've made some rudimentary changes to the article to address this misconception. Mattnz 05:57, 5 April 2012 (UTC)