Linked Questions

1
vote
1answer
14 views

a covariate versus a random effect [duplicate]

I have looked around on cross validated as well as other places but can't seem to find an answer. I'm running a generalized linear mixed-effects model. Y~initial abundance + Treatment + (1|Month) ...
66
votes
1answer
54k views

When to use an offset in a Poisson regression?

Does anybody know why offset in a Poisson regression is used? What do you achieve by this?
20
votes
4answers
17k views

How does a Poisson distribution work when modeling continuous data and does it result in information loss?

A co-worker is analyzing some biological data for her dissertation with some nasty Heteroscedasticity (figure below). She's analyzing it with a mixed model but is still having trouble with the ...
12
votes
1answer
9k views

Identical coefficients estimated in Poisson vs Quasi-Poisson model

In modeling claim count data in an insurance environment, I began with Poisson but then noticed overdispersion. A Quasi-Poisson better modeled the greater mean-variance relationship than the basic ...
11
votes
3answers
4k views

Should I use an offset for my Poisson GLM?

I am carrying out research to look at differences in fish density and fish species richness when using two different underwater visual census methods. My data was originally count data but then ...
3
votes
3answers
5k views

How to estimate and interpret an offset correctly in a Poisson regression?

Assume the following easy example of a glm regression with an offset: ...
9
votes
3answers
372 views

Determining statistical significance of linear regression coefficient in the presence of multicollinearity

Suppose I have a bunch of cities with different population sizes, and I wanted to see if there was a positive linear relationship between the number of liquor stores in a city and the number of DUIs. ...
2
votes
2answers
83 views

Changing the scale in a hypothesis test of proportions

When performing a hypothesis test of a difference of two proportions, does one change the integrity of the problem when changing the scale? To clarify: I want to test the difference in proportions ...
2
votes
0answers
60 views

Is an offset valid or is it endogenous in this count modeling scenario

Theory seems to indicate that an offset should be included in count models if groups are observed for different lengths of time or if they have different levels of exposure. Suppose we are observing ...
1
vote
0answers
31 views

Poisson or Gamma distribution for density or encounter rate data? [duplicate]

I am unsure whether turning count data into density still makes Poisson as the appropriate distribution for modelling. If a given response data are, for example, counts of animals, then such data are ...