# Questions tagged [count-data]

Count data are non-negative integers representing whole amounts.

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### Is it valid to manipulate the unit of time for Poisson distributed counts?

If I have discrete count data measured in minutes (60/minute) that does not fit the Poisson distribution (variance >> mean), is it valid to increase the granularity of that data to seconds if it evens ...
7 views

### JAGS with dependent observations

I have the following model. At every time unit, the arrivals are Poisson. With a Bernoulli probability, I observe either zero of these arrivals or all of these arrivals. If I don't observe anything, ...
29 views

### How to estimate a proportion as a step function of time

There is a black-box mechanical process that, at any time, may be either succeeding or failing. It is known that after an initial disturbance, the process will fail $X\%$ of the time for $N$ seconds, ...
6 views

### Statistical modeling of count data in different regions

I want to statistically model the likelihood of accident categories in different regions. All accidents happened in the timespan of one year. I think I can demonstrate the problem best by reproducing ...
11 views

### Help with multivariate analysis

I'm looking for some guidance on a multivariate analysis that I am trying to run on my data. For context, my response variable is counts of abnormal behaviours displayed during [~60] observation ...
17 views

### Negative Binomial vs. Discrete Survival

I am trying to model a discrete duration variable (number of weeks) and I am not sure which model to use. Many would argue that durations are modeled using survival models. However, in J. Hilbes ...
24 views

### Multicollinearity for Offset Variable?

In a Poisson model, do we need to check for multicollinearity between the offset variable and other covariates? For example, if I offset by population size, would it be problematic to include ...
14 views

### Modelling count data with extreme underdispersion - what distribution?

Suppose we have some count data, and we want to use a model that allows for "overdispersion" or "underdispersion" in the data (i.e., higher or lower variance than the Poisson distribution). Let $X$ ...
11 views

### Statistical tests for periodicity in a histogram

I am trying to analyse the distribution of pairwise distances between data points distributed on a circle. In particular, I am interested in determining whether there is any periodicity in these data....
19 views

### Statistical test to compare predictive measures with count data

I'm reviewing a paper that compares predictors of healthcare demand in terms of hospital visits for several conditions. The authors have used a Pearson's rho to determine which is best, and further ...
31 views

### How to identify outliers in a zero-inflated binomial distribution of count data

I have some data in which the researchers measured the number of times someone lied on a particular day (n=1000). I would like to identify outliers- those people who lied much more than the rest of ...
24 views

### Is a continous distributions valid when modeling count data? And vice versa? when n is high

When looking at the shape of the histogram of a dataset, I always have difficulty discerning if I should model the data based on Poisson or Exponential distribution, as both seems reasonable. Based ...
23 views

### Panel data or separate regression models on count data

I'm trying to find the best way to model count data collected over three years. I have data representing the number of complaints pre-schools in one city has received for the years 2017, 2018 and 2019....
33 views

### Cox model appropriate for my time to event problem?

I am trying to estimate the factors associated with delay in implementation of a policy. I am analyzing the delay, measured by number of days, it took an entity to implement one of three policies, ...
31 views

### Bayesian Statistics - How to weight a Poisson distributed response

I have a Bayesian GLM where the response that I'm interested in is count data. I want to weight the the response by the variance to account for uncertainty in the measurement. If the response was ...
53 views

### Is SAT score a count variable?

It can't be continuous because you can't get a decimal SAT score, right?
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### Can I use Chi square test with the mean of averages instead of total?

I simulated a network-on-chip with different parameters that affect the performance and I'm trying to stablish relations between the parameters. Below I have the average delays for different buffer ...
6 views

### handling spatial auto correlation of case level data in areal units

I'm looking at spatially modelling count data of number of student posts made to an online discussion board for a massive open online course. I have student level data, where the students have ...
17 views

### Probability as a function of age from observations over several years

Hoping someone can help me correct the flaws in my logic. I have a number of water tanks, which may leak. I want to model the probability a water tank leaks given that it has never leaked before as a ...
33 views

### Analysis of time series data with peaks for counts of occurrences

I have time series data that measures the occurrence of insects ona weekly basis during a certain period of several month during several years at several locations. Depending on the insect species and ...
52 views

### Hypothesis testing intervention analysis - pre vs post with expected seasonal change

I have 400 discrete geographic areas of vastly different sizes, where I am recording the number of specific events. Every event is timestamped so I can summerise from daily counts to weekly, monthly, ...
23 views

### Bivariate copula for count and continuous variables?

I'm interested in fit a Copula from my bivariate data with a count variable $Y_{i}$ and a continuous one $X_{i}$. So, let $F(x)$ and $G(x)$ be the margins for the mentioned variables and $C$ the ...
32 views

### Interpretation of zeroinfl vs. glm.nb results

I am trying to test effects of 3 predictors on overdispersed count data with many zeros, and a Vuong test suggested that a zero-inflated neg. binomial model would fit better than a negative binomial ...
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### Appropriate model for count data when response variable minimum value is far above zero

CASE 1: I am trying to model count data; the response variable, y=c(12, 15, 34, 13, 12, 33,....,45) while the explanatory variables are location (binary, rural/urban), marital status, education level, ...
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### modeling response variable that is proportion

I am attempting to model data where the response variable y is a proportion (ratio of counts=successes /(successes+failures) in the range (0,1) the predictors are ...
20 views

### What is a right definition for “nested models” in Zero Inflated Poisson?

Suppose I have 2 models: ...
26 views

### What test do I use for comparing count data for significant differences between two groups of different sizes?

I need to compare count totals between two groups that are of unequal sizes. For example see table: Total injuries includes back/neck injuries. I am looking to see if the back/neck injuries are ...
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### Comparing time series trends of non-linear count data across multiple firms in R

I have data on the number of patent applications per year for 20 years for ten different firms. I am trying to answer the question, "did the number (count) of applications evolve differentially across ...
7 views

### Dealing with count data as both the dependent and independent variable

I have a data set that I want to run multiple tests on, one with the count data as the independent variable in a regression and one with it as the dependent variable in a regression. The count data ...
26 views

### Looking for a discrete distribution with a specific mean-variance relationship

Say we have some counts $Y$ for which the mean-variance relationship is $$Var[Y] = \alpha E[Y] + \beta E[Y]^2.$$ From this, we can say that: If $\alpha = 1$ and $\beta = 0$, then $Y$ can be ...
40 views

### Distribution when count data have no zero counts

My data are monthly counts of samples submitted to a laboratory for testing. The data have no monthly counts of 0 for when no samples were submitted. How should this data be handled? What distribution/...
23 views

### Difference in proportion across study types based on count data from multiple studies?

We have the following situation. We have collected count data from a number of studies. Specifically, we looked at the number of people of each race in each study's cohort. We also collected a number ...
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### Can I treat count data as continuous in Quantile regression?

I have data with the response is the number of dengue disease incidence per year from 2013-2019. The number of incidence per year is a big number, many values of 1000, minimum values is 228. I am ...
18 views

### Two intercepts for zero-truncated negative binomial model using VGAM

I am trying to understand the first and second intercept for the zero-truncated negative binomial regression model I estimated using VGAM. Below is my syntax: mod.negb <- vglm(ED_Visit ~ Male + ...
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### How can I compare coefficient values from two different count models based on the same variables?

I'm running two quasi-Poisson models with the exact same variables, but on samples from two different countries. I'm doing this because I'm particularly interested in seeing whether the relationship ...
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### Count data that has two peaks. How would I model this?

We did an experiment where people came in the lab and engaged in a helping task. They were told they could help with as many puzzles as they wanted to and a peer would finish them. The DV was the ...
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### Test if counts in two conditions are significantly different without knowing the population size

The data are counts of cell structures in different (independent) conditions. For N cells per condition, in which N is different for each condition and unknown, the total number of X and Y structures ...
37 views

### Count Modelling and Rates and Zero Inflation

I am looking for some help modelling overdispersed (zero-inflated negative binomial) count data as a rate. I want to model the survivability of villages in different municipalities given guerilla ...
35 views

### Why use an offset variable as a predictor instead of just converting outcome to a rate?

I am reporting the results of an analysis where we tested the effect of various demographic predictors on the number of counselling sessions undertaken by participants during a clinical trial. I ran a ...
25 views

### Accounting for large absolute differences between entities in panel data regression

I want to estimate the effect of weather on business success by using a a panel data regression. My dependent variable is the daily number of visitors for different entities (for example amusement ...
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### How to interpret the regression co-efficient of a particular variable in a negative binomial regression?

I have the following regression equation with a count variable as the dependent variable and diversity as the predictor. ...
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### MCMC when intervals are irregular

I have a count model that has irregular intervals. It's a collection of some events throughout a year. The data is confidental so I cannot present the actual data but it has the following structure. ...
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### Change in sign of price coefficient between OLS and 2SLS regressions?

I am hoping to estimate demand through two primary specifications, OLS and IV, where the dependent variable is the count of purchases and the primary righthand-side variable is price. In the OLS ...
55 views

### Modelling count differences on irregular lattice

I have the following dataset. I have a time series over an irregular grid where for each position in the grid, there is a variable that for each point in time counts the cumulative difference between ...
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### Is there a statistical test comparing two distributions?

So I have a bar chart with x-axis: microRNA base additions (+1, +2, +3) and y-axis: microRNA counts of patients (each dot is a patient). I would like to compare distribution of base additions for ...
37 views

### Poisson Regression with overload of zeroes SAS

I am testing different models for the best fit and most robust statistics to my data. My dataset contains over 50000 observations, approx. over 99.3% of the data are zeroes - such 0.7% are actual ...
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### Individual Item Probability From Forecasted Counts

My data is a time series, in which I need to be able to predict which day and hour an occurrence of an event is most likely to occur. To answer this question, I have constructed a SARIMA model on the ...
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### Negative Count Variables in Data — modeling migration

I'm trying to explain migration rates in Europe with my regression using pca/pcr in glm. Of course some of the count data has to be negative in regions people move out of. This presents a problem for ...