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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23 views

Why does adding an offset change the coefficients in a Poisson regression?

Suppose I run Poisson regressions but every time the only difference is the offset. Why are my estimated coefficients different? The offset is just like any other predictor in a linear model, the ...
58 views

specifying random effect as offset in logistic glm (R)

I am working on a measurement error model for presence/absence data using a variant of a Monte Carlo EM (MCEM) algorithm for model fitting. As part of this approach, I simulate random effects by ...
22 views

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 ...
36 views

Account for the number of Bernoulli trials in the response and selected predictors of GLM?

I have sampled animals at a number of sites and time points. Each site is sampled up to 4 times a year and is sampled over multiple years. At each site*time ...
48 views

Multiple linear regression LSE when one of parameter is known

Question is the following: For analyzing the observed data, the following regression model \begin{eqnarray} y_i=\beta_0+\beta_1x_{i1}+\beta_2x_{i2}+\beta_3x_{i3}+\epsilon_i \end{eqnarray} is ...
28 views

Admissions per year before and after antibiotics?

I need to compare hospital admissions per year before and after the introduction of antibiotics in 100 patients (antibiotics introduced at various time points in the past). Eg. Before antibiotics: ...
584 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 ...
83 views

Use the offset or use rates as dependent variable in Poisson regression

I'm using a data set of an insurance company, and I want to model the number of claims (counts) as a dependent variable (number of insurance claims, nb_sinistre in this data set). In R I use a glm ...
125 views

How do I fit models with predetermined covariates?

I'm trying to fit a multiple linear regression model. It has 10 variables, 2 of which are specified (e.g. $\beta_4 = 0.5$, $\beta_7 = 0.77$). How do I go about fitting this in R? I need to find the ...
146 views

Statistical analysis of number of flood events

I am given the number of flooding events. There were 9 events in the years 2000-2010, and 6 between 1900-2000. How can one use Poisson to test if the frequency is increasing or not? What other type of ...
149 views

Can a variable be used both as an offset and an independent variable?

I am developing a negative binomial regression model that investigates factors impacting the death rate of animals that are fed. The number of deaths was counted over the course of a feeding season, ...
57 views

Regression with related coefficients

I've worked out that some physical process has the form $y = ax_1 + (1-a)x_2$, and would like to perform regression to find $a$. I thought about multiple regression of $y$ on $x_1$ and $x_2$ and ...
293 views

Estimating conditional effect of logistic regression

I'd like to examine the conditional effect of a new variable, say $\mathbf{Z}$, on a logistic regression previously fit to my response vector $\mathbf{Y}$ using the predictor(s) $\mathbf{X}$. Say ...
26 views

Poisson regression with custom offset and link

I have the following model $$Y \sim \operatorname{Poisson}\left(\frac{1}{1+\exp(\beta X)} E\right)$$ In other words, I have count data for Poisson process with exposure E and rate given by the ...
347 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). ...
40 views

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 ...
24 views

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 ...
43 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 ...
334 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 ...
116 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. ...
270 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 ...
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). ...
27 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 ...
77 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 ...
34 views

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 ...
168 views

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....
333 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 ...
37 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 ...
36 views

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 ...
36 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 ...
53 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 ...
70 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 ...
85 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 ...
101 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 ...
215 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 ...
562 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 ...
125 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 ...
4k views

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 ...
101 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,...
31 views

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 ...
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 ...
156 views

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 ...
646 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?
60 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 ...
491 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 ...
659 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 ...
28 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 ...
451 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 ...
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 ...