No one knows who first said “lies, damned lies, and statistics,” but it’s easy to understand why they said it. It’s no surprise that the bestselling statistics book in history is titled How to Lie with Statistics. While the title is facetious, it is certainly true that statistics can be confusing—consider the word “average,” which can refer to the mean, median, or mode. “Mean average,” in turn, can refer to the arithmetic mean, the geometric mean, or the harmonic mean. It’s enough to make a non-statistician’s head spin.
In fact, a number of people have been confused by the confidence interval WebXPRT reports. We believe that the best way to stand behind your results is to be completely open about how you crunch the numbers. To this end, we released the white paper WebXPRT 2013 results calculation and confidence interval this past Monday.
This white paper, which does not require a background in mathematics, explains what the WebXPRT confidence interval is and how it differs from the benchmark variability we sometimes talk about. The paper also gives an overview of the statistical and mathematical techniques WebXPRT uses to translate the raw timing numbers into results.
Because sometimes the devil is in the details, we wanted to augment our overview by showing exactly how WebXPRT calculates results. The white paper is accompanied by a spreadsheet that reproduces the calculations WebXPRT uses. If you are mathematically inclined and would like to suggest improvements to the process, by all means let us know!