Questions tagged [offset]

A variable with a fixed coefficient of 1. Offsets are commonly used in Poisson regression to allow the modeling of rates instead of counts.

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How to tell if an offset term is used from GLM model summary in Statsmodels?

I am currently working on Poisson regressions with offset terms via the GLM function in Statsmodels, but I think the same issue exists for the GLM function in R as the model summary is quite similar. ...
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Why does removing the offset change the F-statistic of an anova model in R?

When a linear model with only a single categorical variables is defined without an offset, the F-statistic reported by summary() and ...
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Why is an offset needed in Poisson Regression? [duplicate]

Why does Poisson Regression require an offset variable when we model rates instead of a count? In a Poisson Distribution, lambda itself is a rate (e.g. cars per minute). It seems like the Poisson ...
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Is it possible to fit a linear model of y in log scale but with offset in the original scale?

Let's start with simple linear regression with log transformation of the response variable y: $$ \log(y_i) = \beta_0 + \beta_1x_i + e_i$$ (btw, how is this model called? log-linear regression or ...
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Why not always use covariate instead of offset in Poisson Regression? [duplicate]

I've just started studying Poisson regression and came across the two models: $$ \begin{align*} \log{\mathbb{E}(count)} &= \beta_0 + \beta_1x_1 + \beta_2x_2 + \log(T) \\\\ \log{\mathbb{E}(count)} &...
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When are offsets useful in regressions involving literacy or linguistic data?

Motivation Question As the title suggests, I'm looking for examples of offsets in regression that make sense in my realm of research (early child development of reading and writing). To be clear, I am ...
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Negative binomial for catch data with GAM

I work with landing data (kg or tons), which don't follow a normal distribution and are more often than not over-dispersed. I'm trying to obtain a standardized index of abundance using GAM to model ...
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Regression of Purchase Count using Offset Term to Carry Information About Package Size/Count

Hello: I am interested in modelling the purchase rate over time (an integer number of purchases, observed daily, for a number of shoppers) for a collection of 3 different products. The data look a ...
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Use of weights in a binomial model, with the response no longer a proportion

I am studying the factors that influence mosquito feeding behavior. In the experiments, N mosquitoes are exposed to a host for a duration t. At the end of this exposure, we count how many mosquitoes (...
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How to interpret the average rate of NB-GLM when offset is involved?

My question is on how to interpret the coefficients of a negative-binomial GLM that included an offset. My dataset is a clinical trial where patients got one of two treatments (A or B) and stayed in ...
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Prediction of Pure Premium with offset

I'm modeling a pure premium with glm and using an offset term equal to log(exposure). My question is, in R, what does ...
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Understanding emmeans outputs for poisson and negative binomial GLM fitted on count data with or without offset

I fitted a poisson and negative binomial GLM on count data (=larva) and try to explain it as a function of a factor (=modality). However, as the traps used to trap larvae from inflorescences were ...
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Should an offset be removed if the variable doesn't seem to have much influence?

This is about a joint project with a subject matter expert, and I'm the statistician. I will not explain the background and simplify the statistics problem as the background is rather complicated. The ...
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include length text as covariate or offset in negative binomial regression model

I have a dataset that contains the number of devices used to express casual relations in a text. I've constructed a Negative Binomial Regression to estimate the effect of Educational Level (3 levels) ...
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Is it possible to use R-glm-offset as a multiplicative instead of within the exp-function value?

I have a dataset with a number of people at the start of the year and the status at the end of the year (either 0 for alive or 1 for deceased). In the dataset is the mortality probability from a life ...
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Parameter estimate interpretations in lm with offset

I want to analyze flight times of an insect (in function of several weather parameters), but these are done at different distances. One option could be to calculate the speed and analyze this, or what ...
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Is it reasonable to apply different offsets to different species in community analysis?

I am using the manyglm function from the mvabund package. I have a site X species/family dataset of counts. One organism in the community is vastly more abundant ...
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(Ab)Use of offset() in Poisson GLM to weight the damaging effect of counted insect stages

According to A.F. Zuur et al. (2009) in 'Mixed Effects Models and Extensions in Ecology with R', p. 239ff and this post: When to use an offset in a Poisson regression?, ...
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Offset using Poisson distribution

I get everything but the two sentences are confusing me. Offset is a variable that serves to consider the different exposures of different observation. When properly included, the target variable is ...
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How to impose restrictions on a regression using offsets?

An offset is a variable that is included in the regression but without coefficient (i.e. the coefficient is fixed at/assumed to be 1). I want to impose restrictions on my regression and I read that it ...
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Does a GLM where the dependent variable is a rate without offset produce the same result when a count with offset is used?

I have the following two models in Python: ...
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Regression Estimates equal 0, is there something wrong with the model?

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How to account for proportionality of predictors in a poisson regression

I am looking to conduct an analysis to test which variables (diagnosis, ethnicity, level of care) significantly predict the number of self-harm incidents a patient has over 2 years (observational data)...
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Offset variable in a Poisson regression measured with error [closed]

It is known that measurement error in predictors lead to a bias toward zero, and also bias other predictors’ estimates: The effect of covariate measurement error on coefficients in regression with ...
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How to interpret model estimates of a Glmer (poisson) with count data, offset term to get a rate, and random effect

I am trying to apply a glmer on syllable-count data obtained from bird song. I include the record ID as a random factor (1 | rec_ID) due to variation in the number of songs per recording, and consider ...
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Poisson GLM Offset Exposure Question (from a noob)

Hi i am actually not an actuary but I'm currently working on an ML project on insurance pricing. The pricing is calculated by multiplying Claim Frequency and Severity, correct? I'm currently using ...
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how to add offset for Poisson-GPR using GPML package? [closed]

I'm using the popular GPML package in MATLAB for both Poisson and NB regression. Is there any way to add offset as easily as glmfit()? Specifically, assume there are N obesrvations, I want $\log(\mu)=\...
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How should I introduce an OFFSET term for a BINOMIAL response variable?

I have a binomial response variable -proportion of removed fruits, or plant visited or not visited by a frugivore- in a GLMM. I would like to control for differences in the sampling effort (time) ...
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How to interpret coefficents when you have an offset?

I'm measuring counts of birds as a function of the time (in months) across three parks (NP), as well as the presence of carcasses and season. I'm trying to find out whether the population is ...
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How can we incorporate an offset into a software library which performs least squares without offset

Disclaimer: this is not homework, just preparation for an exam I'll be taking How do I incorporate an offset term into a software library that performs least squares (without offset)? Let me give a ...
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Count vs. continuous predictors in Poisson regression with offset

I'm having a conceptual problem related to using different types of predictor variables (i.e., count data vs. continuous data) in Poisson regression. My field method was walking transects and counting ...
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In Poisson models with an offset, should performance metrics (such as deviance) be calculated in terms of raw counts or counts per exposure?

For context, I need some metrics that can compare a standard Poisson regression (with population offset) to a random forest regressor with Poisson criterion. The test predictions for both methods are ...
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How to incorporate offset variable in coxphf()?

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Is "vanilla" random forest regression appropriate when dependent variable is a rate (i.e. per 100 people)?

To add a little more context, I am working with a dataset from which I want to predict the population-normalized count of emergency department visits on county level, with 50+ independent variables. ...
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Offset or weight in binomial GLM - account for distance to road on animal sightings

I am building a species distribution model for an animal, using data collected by community members when they sight this animal. My first step is to fit a generalised linear model with family binomial ...
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Accounting for sampling effort of independent variables in a regression analysis

I would like the test whether the frequency of a cellular structure on a histology section is associated with (binary) patient outcomes. This would be a simple logistic regression of i.e. ...
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Offset in Poisson GLM with log link function where I have values equal to zero

I am trying to build a GLM model (poisson family) using python statsmodels package on train data. The data I have contains categorical values as exogenous variables and numerical values for my target (...
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Does a constant offset term meaningfully influence Poisson GLM?

If my offset term is a constant value, does this change the outcome of a Poisson GLM regression? I have survey count data that we summarize as a rate (Counts/Area-Surveyed). In this case, transect ...
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1 vote
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362 views

Incorporate Weights/Offsets with Nonparametric Models

I am modeling pure premium in R. I have read that pure premiums are usually modeled using a Tweedie distribution (glm). There is generally an offset or weight added to the model, such as an exposure. ...
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Can offset variables be used in binomial logistic regression models?

When I look up what exactly the offset is doing, I only see references to poisson or negative binomial models. Neither of those analyses work for me because I do not want to predict counts. I want to ...
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Inclusion of values that can only be zero in Poisson glmer

I have carried out a biological experiment in which the dependent variable is female propensity to mating, measured as the number of times a female animal accepts a mating attempt from a male. I have ...
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Pair-matched count regression in R with offset?

I need to conduct a pair-matched count regression in R. Specifically, my data looks as follows: ID Exposure Occurrence Area 1 0 7 50 1 1 5 55 2 0 6 70 2 1 8 74 3 0 4 45 3 1 9 62 I need the ...
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416 views

When to use offset in binomial glm

I am trying to model the number of successes in data where the number of trials is not fixed. I am trying to fit a binomial generalised mixed effects model, with the number of trials as an 'offset' ...
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How to include population size in difference-in-differences analysis

I'm trying to estimate the effect of a certain policy intervention on the count of violent incidents in communities which received that intervention, compared to communities which didn't. I'm trying ...
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Poisson regression with offset - help with fit and visualization

My goal is to understand the relationship between the number of worms found in a plot of land and the percent silt that makes up the soil. The plots of land have been investigated to different extents ...
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using per capita or raw counts for epidemiological regression analysis

I have two datasets. To simplify, they look something like this: ...
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Does offset always have to be on log scale with NB GLMM?

I'm using a negative binomial GLMM with R package lme4 to detect differences in time mothers spend feeding before and after birth (inf_cat). ...
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Dealing with singularity and overdispersion in GLMM?

I'm running a GLMM through the lme4 package in R to detect differences in time spent feeding (response) before and after birth (my 2 categories in the variable inf_cat). I started with a Poisson GLMM, ...
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Choosing the best family and link function for a GLM

I'm new to GLMs and I need to do several GLM using a kilometric abundance index (non integer, but calculated from a count) as the dependent variable and several habitat traits as the independent ones. ...
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Do offsets consume degrees of freedom?

In a model with some offset variables (variables with pre-determined regression coefficients), do these variables consume degrees of freedom, with regard of e.g. information criteria? Pro: You can ...
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