Title | Data Dispersion: Now You See it... Now You Don't |
Publication Type | Working Paper |
Year of Publication | 2010 |
Authors | Sellers, K. F., and G. Shmueli |
Series Title | Working Paper RHS 06-122 |
Institution | Smith School of Business, University of Maryland |
Abstract | The most popular method for modeling count data is Poisson regression. When data display over-dispersion, thereby deeming Poisson regression inadequate, typically negative-binomial regression is instead used. We show that count data that appear to be equi-dispersed or over-dispersed may actually stem from a mixture of populations with different dispersion levels. To detect and model such a mixture, we introduce a generalization of the Conway-Maxwell-Poisson (COM-Poisson) regression that allows for group-level dispersion. We illustrate mixed dispersion effects and the proposed methodology via semi-authentic data. |
URL | http://ssrn.com/abstract=1612755 |
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