Many tests for the dispersion parameter in Poisson distribution
Many tests for the dispersion parameter in Poisson distribution.
colpoisdisp.tests(y, alternative = "either", logged = FALSE) colpois.tests(y, logged = FALSE)
y |
A numerical matrix with count data, 0, 1,... |
alternative |
Do you want to test specifically for either over or underspirsion ("either"), overdispersion ("over") or undersispersion ("under")? |
logged |
Set to TRUE if you want the logarithm of the p-value. |
A matrix with two columns, the test statistic and the (logged) p-value.
Michail Tsagris
R implementation and documentation: Michail Tsagris <mtsagris@yahoo.gr> and Manos Papadakis <papadakm95@gmail.com>.
Yang Zhao, James W. Hardin, and Cheryl L. Addy. (2009). A score test for overdispersion in Poisson regression based on the generalized Poisson-2 model. Journal of statistical planning and inference 139(4):1514-1521.
Dimitris Karlis and Evdokia Xekalaki (2000). A Simulation Comparison of Several Procedures for Testing the Poisson Assumption. Journal of the Royal Statistical Society. Series D (The Statistician), 49(3): 355-382.
Bohning, D., Dietz, E., Schaub, R., Schlattmann, P. and Lindsay, B. (1994) The distribution of the likelihood ratio for mixtures of densities from the one-parameter exponential family. Annals of the Institute of Statistical Mathematics, 46(): 373-388.
y <- matrix(rnbinom(100* 50, 10, 0.6), ncol = 50) a1 <- colpoisdisp.tests(y, "over") b1 <- colpois.tests(y) y <- matrix(rpois(100* 50, 10), ncol = 50) a2 <- colpoisdisp.tests(y, "either") b2 <- colpois.tests(y) y <- NULL
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