Probabilistic measures assess the significance of the relationship between objects, determined by some statistic.
Probabilistic χ2 (S22)
References
Legendre P, Legendre L. Numerical Ecology. 2nd ed. Amsterdam: Elsevier, 1998. ISBN 978-0444892508.
The probabilistic Pearson χ2 similarity coefficient is suited to variables expressing frequency or count data. It is the one complement of the probabilities associated with the Pearson χ2 statistic (χP2). Legendre and Legendre (1998) noted a lack of usage of this coefficient in ecology.