Multilevel modelling and time series analysis in ... - ERSO - Swov

2.3.4 CountsIn this case, the dispersion parameter is lower (but also significant), indicatingthat the explanatory variable has accounted for a part of the overdispersion.2.3.4.3. A two-level negative binomial modelAs explained in the Methodology Report (section 2.3.4), another option fordealing with overdispersion in count data is to assume a Negative Binomialdistribution, which includes a more complex variance structure, allowing thusmore flexibility. In order to fit a Negative Binomial model in the data:▪ Create a two-level model including only a constant term in the Equationswindow, as described previously▪ Click on the N (ΩΧ, Β) that appears on the first line of the Equations window,select Negative Binomial from the available distributions and click Done.P r o j e c t c o - f i n a n c e d b y t h e E u r o p e a n C o m m i s s i o n , D i r e c t o r a t e - G e n e r a l T r a n s p o r t a n d E n e r g yP a g e 6 9