Summary statistics

The easiest way to approach this subject is to focus on what we have and what we want to achieve:

1. We have a set of observations which we want to summarize.
2. We want to communicate as much as possible as simply as possible.

Statisticians commonly try to describe the observations in

1. a measure of central tendency like the arithmetic mean
2. a measure of statistical dispersion like the standard deviation
3. a measure of the shape of the distribution like skewness or kurtosis

There are other alternatives, of course. The median and mode are both measures of central tendency. To describe the statistical dispersion, we can use the statistical range, the interquartile range, or the [absolute deviation]?.

The Gini coefficent was originally developed to measure income inequality, but can be used for other purposes as well.

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