Box plots (also called box-and-whisker diagrams) are a concise way of displaying the distributions of a group (or groups) of data in terms of its median and quartiles. This way of describing a data set is commonly called a five-number summary, where the five numbers are the minimum, first quartile, median, third quartile, and the maximum. While less informative than histograms, box plots are helpful for identifying outliers and comparing distributions between groups. Figure 1 provides an example of a box plot showing the distributions of data for two different groups. The whiskers are represented according to their most common method of calculation: the most extreme values falling within 1.5 times the interquartile range (sometimes abbreviated as IQR).

Figure 1 Box plot with whiskers and outliers

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