Linked Questions

24
votes
2answers
29k views

Where does the offset go in Poisson/negative binomial regression? [duplicate]

(First of all, just to confirm, an offset variable functions basically the same way in Poisson and negative binomial regression, right?) Reading about the use of an offset variable, it seems to me ...
1
vote
0answers
130 views

Poisson regression - is offset term required? [duplicate]

I am modeling rates of people given drug $X$ or drug $Y$, working out probability of getting drug. The drug $X$ and drug $Y$ points have been matched on exposure time (person years) to specific drug. ...
1
vote
0answers
97 views

How to take population size into account when running a Poisson regression? [duplicate]

My data takes the following form: Outcome variable = no of suicides (count data) Explanatory variables = Age (grouped into young, middle and old), Gender, Country, Year I am running a Poisson ...
0
votes
0answers
33 views

POISSON REGRESSION AND OFFSET VARIABLE [duplicate]

I am using a Poisson regression model with a count data. More specifically, my dependent variable is the number of children dead. My feeling is that I could use a Poisson model with an offset ...
164
votes
8answers
320k views

In linear regression, when is it appropriate to use the log of an independent variable instead of the actual values?

Am I looking for a better behaved distribution for the independent variable in question, or to reduce the effect of outliers, or something else?
16
votes
3answers
27k views

How to decide which glm family to use?

I have fish density data that I am trying to compare between several different collection techniques, the data has lots of zeros, and the histogram looks vaugley appropriate for a poisson distribution ...
18
votes
2answers
7k views

In a Poisson model, what is the difference between using time as a covariate or an offset?

I recently discovered how to model exposures over time using the log of (e.g.) time as an offset in a Poisson regression. I understood that the offset corresponds to having time as covariate with ...
12
votes
1answer
10k 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
5k 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 ...
12
votes
1answer
12k views

What are the differences between survival analysis and Poisson regression?

I'm working on a classical churn prediction problem using the number of visits of a given user to a site and I thought that Poisson Regression was the right tool for modelling the future engagement of ...
10
votes
3answers
17k views

How to deal with “non-integer” warning from negative binomial GLM?

I am trying to model the mean intensities of parasites affecting a host in R using a negative binomial model. I keep getting 50 or more warnings that say: ...
9
votes
2answers
9k views

Whether to use an offset in a Poisson regression when predicting total career goals scored by hockey players

I've got a question concerning wheter or not to use an offset. Assume a very easy model, where you want to describe the (overall)number of goals in hockey. So you have goals, number of games played ...
7
votes
4answers
4k views

Regression model where output is a probability

I am trying to fit a model, and have the suspicion that what I am doing is not quite right. The data tracks what proportion of people made a decision, and what factors were active when they made their ...
8
votes
2answers
3k views

How can Poisson GLM work with non-count data (rate data)? [duplicate]

My question is related, but not the same as the following question: Fitting a Poisson GLM in R - issues with rates vs. counts Here's some fake data: ...
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: ...

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