Spatial Variance in Ecology - JSTOR
https://www.jstor.org/stable/3545670Another common use of variance in ecology has been ... These indices were largely based on variance to mean ratios (Fisher et al. 1922, Clapham 1936, Blackman 1942). In a Poisson distribution the expected value of the variance is equal to the mean and thereby the ratio of the variance to the mean is expected to be unity.
On the variance mean ratio in models of parasite ...
www.cambridge.org › core › journalsWe study the variance-to-mean ratio of the distributions of parasites among hosts for some models of parasite infection, using the cohort approach. We consider a model with density dependence in parasite mortality, and two different formulations of disease induced host mortality. We show that the distributions of parasites, conditional on host survival, converge to quasi-stationary distributions as host age increases.
Distance, dissimilarity, and mean–variance ratios in ...
besjournals.onlinelibrary.wiley.com › doi › absJul 26, 2017 · Summary. Recent advances employing generalized linear models in ecology have led ecological statisticians to argue strongly for the need to re-evaluate or re-invent commonly used multivariate analyses in ecology to explicitly address the mean–variance ratios of the underlying species data. This paper re-evaluates previous work on the importance of aligning distance- or dissimilarity-based methods with the mean–variance ratios of underlying data and extends the analyses to additional ...
Distance, dissimilarity, and mean–variance ratios in ...
besjournals.onlinelibrary.wiley.com › doi › fullJul 26, 2017 · Recent advances employing generalized linear models in ecology have led ecological statisticians to argue strongly for the need to re-evaluate or re-invent commonly used multivariate analyses in ecology to explicitly address the mean–variance ratios of the underlying species data. This paper re-evaluates previous work on the importance of aligning distance- or dissimilarity-based methods with the mean–variance ratios of underlying data and extends the analyses to additional simulated ...
Index of dispersion - Wikipedia
https://en.wikipedia.org/wiki/Index_of_dispersionIn probability theory and statistics, the index of dispersion, dispersion index, coefficient of dispersion, relative variance, or variance-to-mean ratio (VMR), like the coefficient of variation, is a normalized measure of the dispersion of a probability distribution: it is a measure used to quantify whether a set of observed occurrences are clustered or dispersed compared to a standard statistical model. It is defined as the ratio of the variance to the mean ,
Estimating Population Size & Distribution
www.deanza.edu › faculty › heyerbruceStatisticians have demonstrated that the variance/mean ratio, x, yields a value close to 1 in a randomly dispersed population, because in samples from a random distribution the variance is equal to the mean. Any ratio significantly greater than 1 indicates aggregation, and a ratio less than 1 indicates a trend toward uniformity.