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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Is an offset term necessary for a count model of a behavior where subjects determine trial length?

We are modeling data from a behavioral study in which subject pairs' conversations are coded for specific types of utterances (say "Type A"). Subjects decide when their trial is over and we count Type ...
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1answer
185 views

Residual Deviance and degrees of freedom - Negative Binomial Distribution

I am trying to model count data using python's statsmodels module (Beer's sold at a football stadium as function of visitors, "tilskuer", and weather data). ...
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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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28 views

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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1answer
432 views

Offset option in Proc Logistic (SAS)

What difference does it make in estimation of model equation if a variable is specified in offset option in proc logistic? I know, if I specify a variable in offset option; the variable will be ...
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1answer
319 views

Is the offset_column parameter in H20's random forest algorithm the same as the offset option in SAS Proc Logistic?

I am trying to use H2O in R to run a random forest. http://docs.h2o.ai/h2oclassic/Ruser/rtutorial.html In the documentation, I saw that there is an option for an offset parameter but I cannot find ...
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61 views

What type of data is needed for offset in a Poisson regression model - R

I am trying to do a Poisson regression using the following data, where infant deaths are shown per year for both North and South England. ...
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3answers
238 views

binomial glm with null-hypothesis = 0.33

I have a dataset and need to test if the values are statistical different to 0.33 (=1/3). Flies have the choice between 3 types of berries. So, if they do not care about the type they would lay 1/3 of ...
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19 views

Can I use Poisson regression to model prevalence ratios if I only have information on events?

I often used Poisson regression models to estimate prevalence ratios. However, in these cases my data contained information on the whole population, including events (1) and non events (0). ...
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1answer
23 views

Statistical specification for a Regression with continuous finite range count like data

I am interested in explaining what kind of personal characteristics and work environment variables are associated with sickness absenteeism. My dependent variable is the total number of days a given ...
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63 views

Can I model incidence per 1000 people per month using poisson regression without an offset or using weights?

I am trying to model incidence rates (number of malaria cases per 1000 people per month) over time. I only have the data in the form of rates per 1000 people per month, i.e. I do not know the total ...
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Interpretation of average marginal effect for proportion outcome in Poisson model with offset

To see the association of malaria prevalence with village level risk factors, I ran a Poisson model in r with the prevalence of malaria(y) as a dependent variable, altitude(x1) and Forestation(x2) as ...
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How does offset in XGBoost is handled in binary:logistic objective function

I am working on a mortality prediction (binary outcome) problem with “base mortality probability” as my offset in the XGboost problem. I have used gbtree booster and binary:logistic objective function....
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312 views

POISSON regression with offset variable

Our problem is to determine if there is a relationship between the return on equity of firms (ROE) and the presence (number of indicators used) (Y) of a specific type of indicator showing up in the ...
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27 views

How to fit a gls model with a known slope

i want to fit a gls model (from nlme package) with a specified slope, so i can get the computed intercept for the best fit. I tried to set the slope with an offset. Althogh it works fine with lm, it ...
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Poisson regression on devices that fail during observation period?

I am observing N devices over a period of time $[0,T]$ and counting the number of certain events $y_j$, for each device, during that period of time. I also have some specifications $x_j$ for each ...
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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 ...
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1answer
41 views

Should I include offset in null negative binomial model for comparing to full model?

I'm modeling how various landscape and ecological factors affect the I'd like to evaluate how well my negative binomial model performs over the null. I've specified an offset variable in my model to ...
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1answer
49 views

Offset term in negative binomial regression

I am fitting a simple negative binomial regression model with (Yearly cancer death ~ Offset (Size of population) + Age + Household income). I used the offset term because I want to compare the yearly ...
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1answer
69 views

Logistic regression with coefficients penalized to other numbers

When you penalize logistic regression using l1, l2 or both penalizations, the coefficients are penalized towards 0. I would like to do the same thing but penalizing the coefficients towards other ...
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1answer
79 views

Regression Relationship Between Fraction and Whole Number

I am trying to determine the best regression model to use to determine if there is a relationship between clicks (independent variable) (represented as a whole ...
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1answer
145 views

Negative Binomial Regression: Offset Variable and Dispersion Parameter

My case is that previously it's assumed that the counts of events follows a negative binomial distribution, and the annualized exacerbation rate is 1 with a dispersion parameter of 1.5, and all 500 ...
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534 views

How to calculate robust standard error with offset?

I think the default vcovHC in R's sandwich package does not handle offsets in Poisson models. We see this because robust (heteroscedasticity consistent) standard ...
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115 views

Mixed Effect Model - Roadkill hotspot v. coldspot

This problem concerns road mortality. We have 4 highway sections of varied length that were flagged as problem areas for road mortality with large mammals (moose, deer, elk, and even cows). We used ...
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Offset in NB model produces contradictory results to original data

My (example) data frame is rather simple. I would like to know if there is a difference in numbers between the factors (n=2) within variable X. ...
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Can Weights and Offset lead to similar results in poisson regression?

In "A Practioner's guide to Generalized linear models" in paragraph 1.83 it is stated that: "In the particular case of a Poisson multiplicative GLM it can be shown that modelling claim counts with ...
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80 views

Poisson distribution: how to calculate the expected number of zeros in the presence of an exposure term

I have a dataset each with a line for different products, a count of sales and a number of days on sale. I estimated a Poisson regression to predict sales with an offset term of number of days on sale,...
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1answer
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How to account for different baselines when analysing extremes in time series data

I want to see if Wikipedia articles for topics featured in popular documentaries get a boost in page views on the day the documentary is aired. I then want to see if time on screen is a predictor of ...
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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 ...
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How does Poisson regression (with an offset) relate to Logistic regression?

I have some data I am trying to analyze of how often someone has chosen a given option (which I'll call choice A) vs not choosing it (which I'll call choice B) during a 6 month period. Each subject ...
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1answer
573 views

Simple explanation of offset term for logistic regression

In simple words, how we can force any logistic regression coefficient be 1. Is there any steps/algorithm that used behind offset term?
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1answer
54 views

Count data with “double offsets”?

I am looking into race and homicides in the USA, 1995-2016. I want to look into "trans-race" (victim and perpetrator different races) homicides by race and year. However I want to also include effects ...
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1answer
472 views

Confidence interval for mean of Poisson distribution witih observations of different length

I am struggling with calculating a confidence interval for my data using a Poisson distribution. The context is manufacturing process quality control, and I think that a Poisson distribution is the ...
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571 views

GLM with averaged-count data - Poisson? Negative Binomial? Offset?

I am trying to construct GLMs to explore the relationship between woodpecker abundance and 9 predictor variables (tree density, canopy cover, and so on). My data were collected as counts of ...
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23 views

Include predictions as feature in regression. covariate or offset?

I have a regression setting in which I would like to explore the influence of a given variable on a certain patient condition, given a level of risk for the same outcome, predicted with a more complex ...
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1answer
387 views

Gamma regression and offset term

I'm testing the effect of soil treatments on root and shoot length of seeds of a species. However the seeds had different sizes, which may affect root and shoot development. I have a measure of the ...
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1answer
144 views

Applying offset correctly in an Interrupted Time Series Analysis using segmented regression in GLM in R [closed]

I would like to apply an offset to allow for the population within segmented regression using GLM on count data in R and need to ensure that the formula I am using is correct. Adding offset in 2 ...
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1answer
158 views

gamma mixed model with offset and/or weights

I have some continuous positive data $Y_{ij}$ representing accumulated quantities, where $i$ denotes subject and $j$ a state. Patients are transitioning across states sequentially, but not all ...
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347 views

Poisson regression: how do number of observations and offset affect variance of betas?

Background: In Poisson regression with an offset, like in this answer, @Hong Ooi writes Your underlying random variable is still $Y$, but by dividing by $\varepsilon$ we've converted the LHS of ...
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1answer
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why is XGBoost giving me seriously biased predictions with small nrounds?

I can not put my company data online, but I can provide a reproducible example here. We're modelling Insurance's frequency using Poisson distribution with exposure as offset. Here in this example, ...
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2answers
966 views

Proportion as Dependent Variable or Control for the Denominator in Regression Model

I am a little confused as to which model specifications to use for my question. I have number of technological failures (positive count variable) as dependent variable but I am supposed to control ...
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3answers
979 views

Using glm() as substitute for simple chi square test

I am interested in changing the null hypotheses using glm() in R. For example: ...
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2answers
4k views

Poisson xgboost with exposure

I was trying to model a count dependent variable with uneven exposure. Classical glms would use log(exposure) as offset, also gbm does, but xgboost does not allow for offset until now... Trying to ...
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1answer
838 views

Poisson Rate Regression: Offset? [duplicate]

I'm comparing two groups on the # of hospitalizations they have in a 5 year period. Length of hospitalization stay is highly variable. For example, a patient might have 3 hospitalizations that in ...
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Using an offset term with panel data and unexposed controls

I'm evaluating the effect of a policy change on a count outcome across a number of units over time. I have panel data for 300 units over 20 time periods, with roughly 20% of units exposed to the ...
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1answer
719 views

Poisson regression with offset vs logistic regression

I am thinking to use Poisson regression with an offset variable instead of a logistic regression in case where event is rare, since p (probability of success) is very small and n (sample size is large)...
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1answer
4k views

Difference between: Offset and Weights?

I´d like to know the difference between these parameters when I am using GLM/GLMM/GAMLSS/BETAREG. I have observed a lot of published studies using offset, weights and covariates, however I am not sure ...
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1answer
1k views

Quasi-poisson or negative binomial regression with continuous dependent variable?

My dependent variable is originally count data. Because of several corrections it became continuous variable (originaly my data are pellet-group counts (for estimating deer density), corrected for ...
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2answers
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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: ...
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1answer
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How to interpret glm and ols with offset

I ran a few glm and linear models with an offset. Each row in the dataset is a healthcare user. The data contains medical payments and icu days of each user between 2000 to 2007. As the number of ...