Naked Statistics: Stripping the Dread from the Data

by Charles Wheelan

The most basic measure of the “middle” of a distribution is the mean, or average.

“outliers,” which are observations that lie farther from the center.

The median is the point that divides a distribution in half,

Each percentile represents 1 percent of the distribution, so that the 1st percentile represents the bottom 1 percent of the distribution and the 99th percentile represents the top 1 percent of the distribution.

standard deviation, which is a measure of how dispersed the data are from their mean.

mean. For many typical distributions of data, a high proportion of the observations lie within one standard deviation of the mean

we know by definition exactly what proportion of the observations in a normal distribution lie within one standard deviation of the mean (68.2 percent), within two standard deviations of the mean (95.4 percent), within three standard deviations (99.7 percent),

In some ways, this failure of imagination resembles the military’s periodic mistaken assumption that the next war will look like the last one.

verisimilitude,