# Questions tagged [poisson-regression]

Poisson regression is one of a number of regression models for dependent variables that are counts (non-negative integers). A more general model is negative binomial regression. Both have numerous variants.

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### Why we cannot use linear regression with count data?

We know the counting data can use the Poisson regression or NB regression model, we also know the counting data will violate the normal distribution hypothesis when using Linear regression. I would ...
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### Is aggregated poisson-distributed data still poisson-distributed?

I want to aggregate a dataset which is Poisson-distributed in which each event that occurs is measured at a different time. The data is transformed into transactional data, aggregated on UserID. So ...
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### Does the inclusion of a model offset convert predictor variables from counts to rates?

Does the inclusion of a model offset in Poisson or logistic regression convert predictor variables from counts to rates? Or does it only convert response variables from counts to rates? I understand ...
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### Determine statistical difference of slopes of quadratic relationship in a Poisson regression

I'm looking for a statistical or mathematical way to test the difference between two slopes. Others have asked related questions but my problem is quite particular. I'm running a Poisson regression ...
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### Assess quality of a Poisson regression model on R

we did a Poisson regression because we figured out that our data are count data. Could you kindly explain us where we have to look at in order to understand the quality of our Poisson regression? ...
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### Extension of Lee-Carter model with parametric functions of age and time

A standard model of mortality is the Lee-Carter model where Deaths at age $x$ and time $t$ are given by $D_{xt}\sim Poisson(E_{xt}\mu{xt})$. $E_{xt}$ and $\mu_{xt}$ are, respectively, the average ...
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### Reporting estimates and confidence intervals for levels of categorical variable when word count is limited

I have the following (fictitious) output from a Poisson model (count ~ AgeGroup + other variables): ...
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### Log-linear model for contingency table with no fixed count

I have table of counts of born children with four two-level factor variables (mother smoker/nonsmoker, child born dead/alive, ..). I would like to use log-linear model to understand interactions of ...
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### Literature request: (in)appropriateness of negative binomial for count data with an upper bound

I conducted an analysis where I used binomial logistic regression to analyze x successes in n trials (where n varies between observations) in aggregate (using the R syntax ...
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### The AIC for my Poisson Regression is INF. Does it mean i shouldn't use Poisson regression for my model?

I am trying to create a regression model for this variable (Y) based on 2 categorical variables. So, I created dummy variables to replace them. These dummy ...
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### Predicting vector of counts

I was wondering if there are any models that are similar to Poisson regression, but instead of having 1 count as the target, there is a vector of counts as the target. For example: Typical Poisson ...
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### Overdispersed poisson-distribution and offset --> standard errors?

I am modeling count data using R and doing a fixed-effects/random-effects model and thus limited on functions and therefore cannot use a quasipoisson model or negative binomial distribution, but ...
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### How to choose best multiple regression model (Poisson/quasipoisson/negative binomial)? - R

I'm creating some multiple regression models on some national statistic data checking whether there is a divide in infant deaths between the north and sound of the UK. I have created models for males,...
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### Exposure in Poisson regression [duplicate]

Could somebody explain the concept of exposure in the context of Poisson regression and how it relates to the expected value of a Poisson distributed response?