Linked Questions

90
votes
4answers
38k views

Diagnostic plots for count regression

What diagnostic plots (and perhaps formal tests) do you find most informative for regressions where the outcome is a count variable? I'm especially interested in Poisson and negative binomial models, ...
4
votes
1answer
214 views

How to perform over-dispersion test where null is quasi-Poisson

If I understand correctly, a quasi Poisson regression assumes roughly that $$ \mbox{E}\left[y\left|x\right.\right] = \exp{\left(x^{\top}\beta\right)}, \quad \mbox{VAR}\left(y\left|x\right.\right) = \...
2
votes
2answers
2k views

Forecasting Intermittent Demand with zeroes in times series

I am trying to forecast intermittent demand (slow movers and extreme slow movers). Here's the type of data I am working with weekly data so I cannot really group it has zeroes in time series not ...
2
votes
1answer
490 views

Is it Poisson distributed, and if so, what's its meaning?

I've collected data from my website. The website is about cars. The data are about user reviews and the cars. what we see in the graphs is the probability of some car type (Ford Focus 2008) to have X ...
2
votes
1answer
3k views

Interpreting dispersion of glm.nb

First, I have read this post, this post and this post. All have very useful information. I have three other more specific questions. I have estimated a negative binomial model using the glm.nb ...
2
votes
2answers
499 views

Residual Deviance and degrees of freedom - Negative Binomial Distribution

I am trying to model count data using python's statsmodels module (Beer's sold at a football stadium as function of visitors, "tilskuer", and weather data). ...
1
vote
0answers
64 views

Overcoming model singularity in overdispersed data set

I am analysing a data set that is created from walking transects and recording counts for each group size of animals observed. Each transect has 41 repeats, which was approximately 80% zeros. However, ...
1
vote
0answers
370 views

Why do different negative binomial regression functions produce different coefficients, p-values

I have a dataset consisting of number of mutations per person. Covariates I think may be related are age and source of the DNA sample. I want to determine whether the disease the person has ...
0
votes
1answer
1k views

Effectively using coefficients from poisson regression

This is maybe annoyingly easy for some, but I am completely new to regression. As an example, I shall use the data set in R, called mtcars. I am interested in the ...
0
votes
0answers
105 views

Choosing the right model: Poisson, Quasi-Poisson and Negative Binomial?

[Edit] I am working in R. I am investigating the effects of weather on restaurant demand. My DV is the number of restaurant visitors per hour, my IVs are five weather variables and all other ...
0
votes
1answer
40 views

How to model count data in which events are not independent

I have data on the number of hospitalizations over one year in patients with chronic obstructive pulmonary disease, and I need to estimate the difference in the number of hospitalization between two ...