# Questions tagged [poisson]

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### Spatial regression models for counts

I'm trying to model count data with both a Poisson regression model and a Negative binomial model. These counts are referred to the spread of a disease in each spatial unit area (I have 110 obs). I ...
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### Determining if data is zero-inflated

I am attempting to use the check_zeroinflation() function from the performance package in R to determine if my count data is zero-inflated and I was wondering what the ratio in the function output ...
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### Why does the sum of Poisson distributed random variables have a Poisson distribution but the average of the variables do not?

From a biology background and not strong in statistics. From what I have read the sum of Poisson distributed random independent variables have a Poisson distribution but the average of these variables ...
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### Statistical test to see if there has been a significant increase in calls each year

I am undertaking a study that looks at the annual calls to a poisons information centre. I have the total number of annual calls for each year from 2009 - 2018. I was wondering what is the best test ...
44 views

### Poisson Process Conditional Probability computation

Given $N(t)$ a Poisson Process with generation rate $\lambda$ with $t_1<t_2$ and $N_2>N_1$ I'm looking for a way to express the following probability: $$P[N(t_2)>N_2|N(t_1)<N_1]$$ In ...
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### How to estimate the intensity rate $\lambda$ of a Cox Process

In a Cox Process, or doubly stochastic Poisson process, the intensity rate itself is a stochastic process that varies across space or time. Let us assume that the intensity rate has the following form ...
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### Why would you want to fit/use a Poisson regression instead of Negative Binomial?

Given that Poisson is a special case of Negative Binomial which seems to just make error more likely in the case of overdispersion, without offering any real benefits, why would you fit a Poisson ...
105 views

### leverage() diagnostic test not supported for glmmTMB models in r

I am using a glmmTMB to look at the effect of numerous variables on how far individuals travel (distance). The example below is ...
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### The difference of Standard Error from vcov() and sigma() of poisson regression by glm in R

I got the SE of glm(y=x) by the following program. But I couldn't get the same SE as vcov() and sigma() by the following program glm(y ~ x, family=poisson(log)). I can't understand the difference of ...
63 views

### Poisson confidence interval in poisson.test similar

Here is my data. I observed 3 intervals (for example each 1 month long). In each interval my random variable assumed the following values 10, 15, 12. I would like to estimate confidence interval for ...