Others are semi-interquartile range (Q) and the Index of Dispersion (D).

Range, semi-interquartile range, standard deviation.

The semi-interquartile range, i.e.

The range is an informative tool used as a supplement to other measures such as the standard deviation or semi-interquartile range, but it should rarely be used as the only measure of spread.

Calculate, compare and interpret range, quartile deviation, standard deviation and co-efficient of dispersion.

Several are standard statistics that are used elsewhere - range, standard deviation, variance, mean deviation, coefficient of variation, median absolute deviation, interquartile range and quartile deviation.

In a further non-standard bivariate plot, Buller & mcmanus (1972) suggested using the central sub-population, which frequently spans over half of the distribution, to provide a metric quartile deviation measure to plot against the median diameter.

As a measure of the characteristics of the sediment they are of limited value, but as a method of characterizing the central segment of a curve the Trask Sorting coefficient or its equivalent, the phi Quartile Deviation may have some value.