A median of the minds: to be above average, know what mean means (and some other stats)

Benchmark metrics typically come in three forms: averages, medians and weighted averages. Think of 11 law departments each pooling data on their percentage of certified paralegals. For the average, total the 11 percentages and divide by 11.

For the median, rank the 11 figures from highest to lowest and pick the middle one (or average the two middle ones if there is an even number of figures).

For the weighted average, add up all the paralegals of the 11 departments and all the certified paralegals and divide the certified total by the paralegal total.

A variation sometimes seen, which avoids the anomalous outliers that can distort averages, yet draws on more of the data than the median, might be called the average of the middle. After ranking the figures, drop the top and bottom quartile (25%) and calculate the average of the middle fifty percent. So, roughly speaking, drop the top two percentages and the bottom two percentages and average the middle seven.

One other statistical descriptor is common. The range comes from subtracting the highest and lowest percentage.

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