Count data with high frequencies of zeros are found in many areas, specially in biology. Statistical models to analyze such data started being developed in the 80s and are still a topic of active research. Such models usually assume a response distribution that belongs to the exponential family of distributions and the analysis is performed under the generalized linear models' framework. However, the generalized additive models for location, scale and shape (GAMLSSs) represent a more general class of univariate models that can also be used to model zero inflated data. In this paper, the analysis of a data set with excess of zeros and overdispersion already analyzed in the literature is described using GAMLSSs. The specific GAMLSSs' tools used enhanced model comparison and eased the interpretation of results.

The standard procedures for analysing hierarquical or grouped data are by (non)linear mixed models or generalized mixed models. However, the generalized additive models for location, scale and shape (GAMLSSs) also allow different types of random effects to be included in the model formulation. Even though already popular in many areas of research, this type of models have not been found to be used for mixed modeling purposes yet. Therefore, this paper describes the analysis of an experiment with plants' growth using mixed GAMLSSs, comparing it to a linear mixed model approach.