The upper and lower hinges are descriptive statistics of a set of data values, where is of the form with
, 1, 2, .... The hinges are obtained by ordering the data in increasing order , ..., , and writing them out
in the shape of a ``w'' as illustrated above. The values at the bottom legs are called the hinges and (and the
central peak is the Median). In this ordering,

For of the form , the hinges are identical to the Quartiles. The difference is called the H-Spread.

**References**

Tukey, J. W. *Explanatory Data Analysis.* Reading, MA: Addison-Wesley, pp. 32-34, 1977.

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1999-05-25