Measurement of non‐randomness in spatial distributions

Abstract

SummaryThe measurement of departure from randomness in spatial distributions has widespread application in ecological work. Several “indices of non‐randomness” are compared with regard to their dependence on sample number, sample size and density. Criteria for the best choice of index for specific situations are discussed. A new coefficient Cx is proposed for use with positively contagious distributions and tests of significance are given. When Cx and another index (S2/m−1) are used for positive and negative contagion respectively, values ranging from −1 through 0 (random) to +1 are obtained, regardless of sample number, sample size or density.