from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The presence of greater dispersion in a data set than would be expected according to the statistical model in use.
Moreover, I seem to recall that there might be some overdispersion present, so something like negative binomial marginals might be better.
When the slope is less than one (dashed line in the bottom panel) this shows a bias towards lower phylogenetic overdispersion and phylogenetic clustering.
When the slope is greater than one (dashed line in the top panel) shows a bias towards higher phylogenetic overdispersion and phylogenetic clustering.
Thus negative NRI and NTI values indicate a high level of phylogenetic overdispersion.
Distributions of numbers of contacts are discrete distributions and usually display a high degree of overdispersion with some persons having large numbers and many persons having low numbers of contacts.
Median IBS and overdispersion factor (lambda) of the quantile-quantile plot for each population pair (a), and values of chi-square test statistic (b) and expected mean IBS (c) for combinations of allele frequencies in two populations.