Whittermore's statistic is defined as follows:
$$W=\frac{n-1}{n}r^{'} D r$$
where \(r^{'}=[O_1/O_+, \ldots, O_n/O_+]\) and \(D\) is a distance matrix between the centroids of the areas.
It can be used to assess whether the region under study tends to cluster or not.
Whittermore, A. S. and Friend, N. and Byron, W. and Brown, J. R. and Holly, E. A. (1987). A test to detect clusters of disease. Biometrika 74, 631-635.
DCluster, whittermore.stat, whittermore.boot, whittermore.pboot