Interdecile range
In statistics, the interdecile range is the difference between the first and the ninth deciles. The interdecile range is a measure of statistical dispersion of the values in a set of data, similar to the range and the interquartile range, and can be computed from the seven-number summary.
Despite its simplicity, the interdecile range of a sample drawn from a normal distribution can be divided by 2.56 to give a reasonably efficient estimator of the standard deviation of a normal distribution. This is derived from the fact that the lower decile of a normal distribution with arbitrary variance is equal to the mean minus 1.28 times the standard deviation.
A more efficient estimator is given by instead taking the 7% trimmed range and dividing by 3 ; this yields an estimator having about 65% efficiency. Analogous measures of location are given by the median, midhinge, and trimean.
