title: A MANOVA test for multivariate lognormal observations with a spike at zero, with application to ecological niches of South Africa.
abstract: We develop an asymptotic likelihood ratio test for multivariate lognormal data with a point mass at zero in each dimension. The test generalizes Wilks' lambda and Hotelling T-test to the case of semicontinuous data. Simulations show that the resulting test statistic attains the nominal Type I error rate and has good power for reasonable alternatives. We conclude with an application to exploration of ecological niches of trees of South Africa.
authors.affiliation: Department of Public Health and Infectious Diseases, Sapienza - University of Rome, Piazzale Aldo Moro, 5, 00185, Roma, Italy.
authors.forename: Alessio
authors.initials: A
authors.lastname: Farcomeni
mesh_terms: D055669:Ecological and Environmental Phenomena; D015999:Multivariate Analysis; D013019:South Africa; D013223:Statistics as Topic / Q000379:methods*
keywords: Excess zeros; Hotelling T-test; Likelihood ratio test; Wilks’ lambda