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interquartile range

(NL: interkwartielafstand (IQR))

The interquartile range (IQR) of a sample or population is calculated as:

\[ IQR = | Q_3 - Q_1 | \]

With \(Q_3\) the third quartile and \(Q_1\) the first quartile.

Between \(Q_1\) and \(Q_3\) you will find 50% of the observations in the sample.

The interquartile range is a measure of dispersion for quantitative variables. It is less sensitive to outliers than the standard deviation and is therefore better suited than the standard deviation for variables that are not normally distributed.