Please use this identifier to cite or link to this item: https://hdl.handle.net/10419/123468 
Year of Publication: 
2014
Series/Report no.: 
WWZ Discussion Paper No. 2014/13
Publisher: 
University of Basel, Center of Business and Economics (WWZ), Basel
Abstract: 
The rootogram is a graphical tool associated with the work of J. W. Tukey that was originally used for assessing goodness of t of univariate distributions. Here we show that rootograms are also useful for diagnosing and treating issues such as overdispersion and/or excess zeros in regression models for count data. We also introduce a weighted version of the rootogram that can be applied out of sample or to (weighted) subsets of the data, e.g., in nite mixture models. Two empirical illustrations are included, one from ethology, the other from public health. The former employs a negative binomial hurdle regression, the latter a two-component nite mixture of negative binomial models. A further illustration involving underdispersion and an R implementation of our tools are available in the R package countreg.
Subjects: 
rootogram
visualization
goodness of fit
count data
Poisson regression
negative binomial regression
hurdle model
finite mixture
Persistent Identifier of the first edition: 
Document Type: 
Working Paper

Files in This Item:
File
Size
309.91 kB





Items in EconStor are protected by copyright, with all rights reserved, unless otherwise indicated.