R: Tests for the dispersion parameter in Poisson distribution

Tests for the dispersion parameter in Poisson distribution {Rfast} | R Documentation

## Tests for the dispersion parameter in Poisson distribution

### Description

Tests for the dispersion parameter in Poisson distribution.

### Usage

    poisdisp.test(y, alternative = "either", logged = FALSE)
    pois.test(y, logged = FALSE)

### Arguments

`y` | A numerical vector 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.

### Value

A vector with two elements, the test statistic and the (logged) p-value.

### Author(s)

Michail Tsagris

R implementation and documentation: Michail Tsagris <mtsagris@yahoo.gr> and Manos Papadakis <papadakm95@gmail.com>.

### References

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.

### See Also

`poisson.mle, negbin.mle, poisson.anova, poisson.anovas, poisson_only`

### Examples

    y <- rnbinom(500, 10, 0.6)
    res<-poisdisp.test(y, "either")
    res<-poisdisp.test(y, "over")
    res<-pois.test(y)

    y <- rpois(500, 10)
    res<-poisdisp.test(y, "either")
    res<-poisdisp.test(y, "over")
    res<-pois.test(y)

[Package Rfast version 2.0.0 Index]