Count data

Check for overdispersion

1. There is overdispersion.

   • Is overdispersion due to excess zeros?

     • Do the zeros seem to come from a different process?

     • 
       

   • If there is overdispersion, use one of the following (fit both and use AIC to determine best f it)

     • zero-inflated Poisson distribution

       • assumes zeros generated by a diff process

     • zero-inflated negative binomial distribution?

2. There is no overdispersion:

   • Use one of the ff

     • Poisson distribution

3.