New quarterly report. In addition, we've tracked results since August 1999 to show whether an ISP's ranking has spiked for one month or is consistent. Coming in a close second is BellSouth, which performed above average in five out of nine categories. The data for this report comes from Visual Networks. First, we derived the standard deviation of the numbers in each performance category.
Standard deviation is a measure of how far the numbers in a series diverge from each other.
For each category in which an ISP performed better than one standard deviation from the industry mean, we awarded it one point. If the ISP did better than two standard deviations from the mean, we awarded it two points. Similarly, if an ISP did worse than the industry mean by more than one standard deviation, we took a point away from its score. If it did significantly worse, meaning two or more standard deviations, we took away two points. We started with a baseline of 12 points, so if an ISP scored 0 points it ended up with an adjusted score of 12.