Disclaimer: My company also does web performance analytics. I did a talk a couple of years ago on the statistics of web performance where I cover things like m

Disclaimer: My company also does web performance analytics. I did a talk a couple of years ago on the statistics of web performance where I cover things like median, arithmetic mean, geometric mean, margin of error and sample sizes to carry out proper data analysis. Slides available here: http://www.slideshare.net/bluesmoon/index-3441823 http://www.slideshare.net/bluesmoon/index-3441823 To zashapiro's point about Geometric Mean... while it tends to be superior in the ideal case where the distribution is perfectly Log-normal, on average, most distributions tend to sway from a perfect log-normal. The median gives you a slightly better measure of central tendency in this case. Secondly, there's the problem with user perception of geometric standard deviation (and consequently margin of error). Unlike arithmetic standard deviation which is +-, the geometric standard deviation is */, which means it's not visually symmetric... humans have an easier time visualizing additive symmetry than they do with multiplicative symmetry. At LogNormal.com, we track the median, arithmetic mean, geometric mean a whole bunch of percentiles and margins of error and a complete distribution curve.