Q statistic

This infrequently-used diversity measure was proposed by Kempton and Taylor (1976). It measures the interquartile slope of the cumulative abundance curve and is estimated by :

where                nr = the total number of species with abundance R;

                       S = the total number of species in the sample;

                       R1 and R2 the 25% and 75% quartiles of the cumulative species curve;

                       nR1 = the number of individuals in the class where R1 falls;

                       nR2 = the number of individuals in the class where R2 falls.

This index has been little used, probably because of the difficulties of computation. It seems worth considering; see Magurran (2000).

To compare two indices see Testing for significant differences between indices.

A simple plot of the way the index changes between samples is displayed by clicking on the Graph tab on the output window.