= Interquartile range
{title2=$\mathrm{IQR}=Q_3-Q_1$}
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= IQR
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The <interquartile range> measures the width between the lower and upper <quartiles>, in the same units as the observations. It describes central spread rather than the distance between the observed extremes. In our toy <box plot>, $\mathrm{IQR}=6.25-2.75=3.5$; moving the largest value from $20$ to $200$ would leave the <quartiles> and <interquartile range> unchanged under the chosen rule, because the <order statistics> used in their interpolation would not change.
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