# Tagged Questions

Variables that are counts (non-negative integers) often have an excess of zeroes. Zero-inflated regression models (e.g. zero inflated Poisson, zero inflated negative binomial) are designed to deal with this. Less commonly, continuous data can have this issue, and there is zero-inflated normal ...

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### How to Test for Some Basic Assumptions of (Zero Inflated) Negative Binomial?

I am currently working with a T dominant panel --time-series cross-section dataset-- that has N = 8 (eight European countries) and T = 28 (28 quarters for each country). The dependent variable --...
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### Which test can I use to compare two count data means with a lot of zeros?

Suppose I have two count datasets, lets say the count of tigers across different years at two places. Now for most of the years we have 0 tiger sightings. For eg. ...
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### Predicted values in negative binomial model with 0-inflation

My count data are zero-inflated, for which I utilized glmmADMB. ...
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### Interpreting the Vuong test and its corrections - choosing between ZINB and NB

I have a problem with the data for my MSc thesis. I collected count data with two methods of forest monitoring and now I want to compare them. I divided my sample into 50m segments (n>500) and summed ...
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### Chosing the right test for weekly disease counts

I am using STATA to analyze count data (weekly disease counts), and I am trying to pick the best test between Poisson, negative binomial and zero-inflated Poisson / negative binomial but I am not sure ...
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### Sensitivity analysis on constants: logit transformation for ANOVA

I have categorical looking-time data (looks to visually presented items A, B, C and D over a number of seconds), containing 0s and 1s. I want to compare groups (adults, children; n=~30 for each group) ...
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### Relationship between two (zero-inflated) count variables

TLDR: How can I model the relationship between two count variables that are both dependent on the same third, unobserved, continuous variable. Detail I am interested modelling the effect of an ...
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### Comparing count data models?

I am trying to fit Negative binomial, Zero Inflated Negative Binomial, Negative Binomial Hurdle, and Random effects negative binomial. Here is the value of AIC for different model: Negative Binomial: ...
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### Maximum Likelihood Estimation on Zero-Inflated data using Constraint

I have written a function that evaluates the log-likelihood of Zero-inflated Beta Binomial data: ...
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### How to mitigate risks for an oversampled training and validation set for a Zero-Inflated Poisson model?

I have a data set, with training, validation, and test already decided for me. It is a mailing list response project so it has a lot of zeroes representing no response, and some ones representing a ...
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### How to improve the fit of a zero-inflated, negative binomial glmmADMB model

I have been trying to fit count data that is zero-inflated and overdispersed using generalized linear mixed models. My research led me to the glmmadmb function in the glmmADMB package. I am fitting ...
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### How to interpret negative fractional incidence risk ratio?

I'm using a Zero-Inflated Poisson regression to model a count outcome with lots of zeroes. However, I'm having trouble understanding estimates in the count model that are both negative and smaller ...
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### Estimating unconditional effects in double hurdle models

I trying to implement a double hurdle model in JAGS and am struggling to understand how to estimate the unconditional effects of each predictor variable on the count process. I have implemented the ...
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### How to calculate variance contribution in a Zero-Inflated Poisson regression?

I was wondering if anyone has an idea on how to calculate the contribution to variance of each independent variable in a Zero-Inflated Poisson. How would it even work if you actually have two models ...
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### Glm planned comparison fail to compare identical samples

I am dealing with several treatments, binary dependent variable and lots of zeros. When running a glm with pairwise comparison the model fail to compare two different treatments that have actually ...
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### Double Hurdle model with continuous DV and two sources of zeros

I want to regress a data set that contains a lot of zero's (~55%) and is determined by a typical 2-stage decision process generating the zeros: Consumer decides to apply for a bank loan or not (0-1) ...
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### Help with zero-inflated generalized linear mixed models with random factor in R

My study has a complicated design and I am not sure if I am modeling my zero-inflated data correctly. I have seed abundances and seedling abundances for 11 species. I have one main "treatment" with ...
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### zero-inflated negative binomial in Stata

I am trying to run a zero-inflated negative binomial analysis in Stata (zinb). My question/problem is this: the model's convergence seems dependent on which and how ...
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### Right censored data, abundant in zeros for regression analysis

I am looking at conditioning to stimuli and there in the time taken to perform a certain task. The IV for this data is Conditioning periods ranging from 1-34 periods and the DV is the time taken for ...
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### Modelling zero-inflated continuous data

I'm currently trying to apply a linear model (family = gaussian) to an indicator of biodiversity that cannot take values lower than zero, is zero-inflated and is continuous. Values range from 0 to a ...
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### SEM with zero-inflated outcome

I'm working on a project and my advisor wants me to do SEM in MPLUS because we can do latent modeling, but I have no clue where to start. I've only ever done regressions but I said I'd be up for ...
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### Set G in prior for MCMCglmm in R

I am new to the MCMCglmm package in R, and rather new to glm models in general. I have a dataset of species traits and whether or not they have been introduced outside of their native range. I would ...
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### Multicollinearity in Zero Inflated Negative Binomial Regression

I am trying to model counts govt, based on the counts lp,const,...
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### Modeling with zero-inflation models for prediction

Below is the summary of my dataset: ...
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### Prediction from Zero Inflated Models?

I have fitted a two stage generalized additive model to zero inflated data ("hurdle model"). I am modeling fishery spatial data (catch rates) as a function of different environmental variables (...
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### Regression problem in data with many zeroes

This is my first question here, so please bear with me. I am working on a regression model to estimate the long term value of users of a certain website. For example, I would like to estimate the ...
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### Regression coefficients versus marginal probabilities

I ran a negative binomial regression model and found significant coefficients for several key variables. I also ran the model as a zero inflated negative binomial model, and didn't find significance. ...
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### How to model these data? (zero inflated, positive skew,

- The variable depicted in the histogram is a sum of 11 items. Each item asks about the frequency of occurrence of a particular type of event (a negative consequence of drinking) on the following ...
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### Canonical Link Function in Zero-Inflated Poisson Model

For a zero-inflated Poisson model, I understand that the Poisson Model uses the canonical link of log(mu). For the logistic portion of the model, I usually see the equation written as logit(phi), and ...
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### Zero-inflated Poisson regression Vuong test: Raw, AIC- or BIC-corrected results

I'm analyzing count data for a set of ten species and found that for the five species with highest detection rate, the zero-inflated poisson (ZIP) regression fits the data significantly better than ...
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### Zero-inflated Poisson regression: how can I calculate contrasts for BACI (Before-after-control-impact) experiment?

I am analyzing count data with a lot of zeros and found that although the data do not fit a poisson glm, they fit the zero-inflated poisson (ZIP) regression significantly better than the standard ...
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### Relationship between two zero-inflated counts varying in space

I have two variables where each observation represents counts at some point in a discrete 1D space (along an RNA sequence). The space is finite, and the counts are highly zero-inflated compared to a ...
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### estimating probably of false zeros using ziP GAM

I pulled the code below from Zuur et al. 2009 (was used to estimate probability of false zeros with a zeroinf() model) and applied it to a ...
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### Statistical Procedures in Heavy Zero Density Data

How do procedures such as Principal Component Analysis, Logistic Regression, Cross Validation perform under Zero under Zero Heavy Data? Are they sub-optimal or simply inadequate?
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### Dual Quasi-Newton Optimization on Zero Heavy Data (in SAS)

I am using PROC FMM in SAS, in attempt to use hurdle models on a data set with many zeros. There is one response variable and it's continuous, there are ~90 predictors (continuous - but contain many ...
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### Modelling Data with Many Zeros - Principal Component Analysis vs Zero Inflated Models

I have a data set (many continuous predictors, single response variable that is also continuous) with many zeros. I first used PCA and found the results to be very helpful. I further thought that the ...
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### Zero-inflated models how to get predicted values = 0 stata

I'm fairly new at Stata and this is the main reason of my question. I did a longitudinal zero-inflated poisson model: ...
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### zero inflated negative binomial versus earth to describe data

Hi is earth function in the earth package appropriate for zero inflated negative binomial data? Is the apparent exponential curve an artifact of erroneous application by me? Opinions very welcome. I ...