A long-tail distribution is a form of probability distribution or empirical histogram of values, where the number of extremely large elements may be sufficient to make a major difference to common measures such as the mean or {[standard deviation}}. A common example of a long-tailed distribution is the power-law distrubution often encounterd in network data such as social media connections or web links. Income distrubutions in most soieties are less extreme than the power law, and usually has a well-defined mean but still have effectively unbounded variance. Note that some distributions such as the Normal distribution may have a long tail in the sense that there is the potential for a few very large values, but these are exteremely rare.
Used on pages 141, 147, 169, 210
Long-tail distribution
Long tail of large incomes. Source: Statistics for HCI~\protect\cite{dix2020stats}, adapted from Office of National Statistics~\protect\cite{ONS14}