A Significance Test for Morisita’a Index of Dispersion and the Moments when the Population is Negative Binomial and Poisson
The moments of Morisita’s index of dispersion are derived assuming the observed counts follow negative binomial and Poisson distributions. The moments are expressed as truncated infinite series. Bounds are placed on the truncation error. The rate of convergence to normality of the index appears to be slow for populations with low mean density. A significance test for the comparison of the dispersions of two populations is suggested. Data from a census of the presence of the southern green stinkbug (Nezara Viridula) on three crops are used to examine the effect of sample size and quadrat size on the power of this test and on confidence interval coverages.
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