# Tagged Questions

Count data are non-negative integers representing whole amounts. When such data are the dependent variable in a regression, Poisson or negative binomial regression may be appropriate methods. One common problem is "zero-inflation" (where the proportion of zero values is greater than predicted by a ...

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### Help running a Difference in Difference

I have a simple linear DiD model for patent count data $$patent_{ut}=\beta_0 +\beta_1 grant_u +\beta_2ptreatment_t +\beta_3 interaction_{ut}+error_{ut}$$ where u denotes a university and t denotes ...
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### Should OLS always have a lower RMSE than Poisson Regression?

I'm working on building a predictive model for the number of singles a hitter in baseball generates over the course of a single game. Since the number of singles a hitter scores per game is count data ...
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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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### Poisson process (discrete counts) measured over varying time interval with many zeros

I am modeling forest inventory data. Forest plots are visited every 5-10 years. New trees that cross some threshold diameter between census intervals are classified as 'recruits' and counted. ...
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### Relationship between Poisson, binomial, negative binomial distributions and normal distribution

When we have to define discrete counts distributions, we usually use : Poisson distribution, if mean = variance Binomial distribution, if mean > variance Negative binomial distribution, if mean <...
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### Sample size determination for estimating a count

I want to estimate a simple variable: "**how many times my website is visited in 2015?". Suppose that I cannot count all visits to my website (it is expensive!), but I can count the connections on ...
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### Obtaining AICc weights after glm.nb

I am performing negative binomial regression using glm.nb() function from MASS package and calculating AICc using package "AICcmodavg". I need also to obtain the (AICc) weights using aictab() function ...
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### Most appropriate test for count data

So I've performed an experiment whereby I had 12 1km transects. 6 of these were along rivers running through agricultural land and 6 through woodland. These were arranged in pairs so that each agri ...
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### Count regression for a response that have a strict upper bound

I wonder what is the optimal way to conduct count regression when the response variable has a strict upper bound. For example, I would like to relate some predictors to how many lung lobes are ...
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### Standard error of mean for overdispersed count data

I have count data from survey transects at several sites (typical n ~10). I am interested in whether the sample mean exceeds a threshold at [1-alpha]% confidence level (...knowing I have low power), ...
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### Count data that can take only 4 values

What is a good model for estimating a regression whose count dependent variable that only has 4 values: 0, 1, 2, 3? The variable is not truncated, it is just something that can only be from 0-3. I've ...
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### Searching for a good book on count data

I am seeking recommendations for a good book on count data, with clear explanations of topics like Poisson regression. The level of the book should be suitable for a graduate math and statistics ...
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### Count data regression model formulation

I am working on one of the discrete probability distribution having pmf as P(x)={p^log(1+x^c)}-{p^log(1+(x+1)^c)} 0<p<1; c>0; x=0,1,2,. It fits well ...
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### Normalization of count data of time periods with different length

I have count-data from two time-periods which differ in length. The event I'm counting is in both periods the same kind of event. Period 1 is 120 hours Period 2 is 48 hours At the end I have ...
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### Dependent variable is count data, which method to use?

Which method should I use to analyse the relationship between count variable (absent days) and other 4 variables? Should I standardise Size variable? Please recommend some further literature/ ...
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### One-sample t-test on count data

I’m working with sports performance data (ice hockey). The question I’m trying to answer is: Does the number of duels player A won in a specific match differ significantly from the mean number of ...
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### Modeling count data over years through poisson regression

I have the following problem. I am trying to use the poisson regression on my data, which look like this: ...
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### What regression model is the most appropriate to use with count data?

I am trying to get a little into statistics, but I am stuck with something. My data are as follows: ...
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### Validation of prediction interval for count data

I have developed a random-effects (frailty) survival model for repeated events which enables calculating individual-specific mean and prediction interval for the cumulative incidence (rate) of future ...
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### Formula logic of Croston's method

In an article of Willemain et al (2014) (doi:10.1016/S0169-2070(03)00013-X) do they give an explanation of the Croston's method in which they use the following equations: How can the forecast of <...
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### Measure of central tendency for periodic variable (hour of day)

I have a dataset that shows, for each group, the number of times a certain action was completed during each hour of the day. ...
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### Which statistical test is most appropriate for my count data?

I did a study looking at how the number of times a specific behaviour is performed during a courtship ritual is affected by temperature treatment, while trying to control for the body size of the male ...
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### Forecasting Poisson, accuracy and prediction intervals

I'm trying to forecast Poisson data, divided in groups, of 1-26 months of data, depending on the group. Of the pooled data ...
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### Analysis of Categorical and Likert-Like Survey Data

I'm about to have data from intercept surveys conducted in parks. The goal of the survey is to determine which characteristics of parks users find most important to park quality (do they care a lot ...
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### Selecting Link Function for Negative Binomial GLM

I'm trying to model insect abundance data with a variety of vegetation/site related covariates. Because it is count data that is over-dispersed, I've decided to use the negative binomial distribution. ...
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### Modeling different rates with same offset

I'm working on my PhD and trying to analyze some data and would appreciate anybody's two cents. I'm going to trying to explain my issues with a simplified example below. Generally, I am trying to ...
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### Can I sum up my count data instead of performing some repeated measures analysis?

I want to analyze establishment of plants in created gaps (plots): I have 10 treated plots, which are divided into an outer section and an inner one and I have been looking at these plots over a ...
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### Poisson regression with days per week as the DV

I am estimating a poisson model (and negative binomial for comparison) with the number of days in a week that a person made a fishing trip as the dependent variable. The range of this variable is ...
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### Smoothing weekly count data

I have samples of weekly count data for shoppers. The counts are based on hourly observations For example, for week 1 the hours of observation were Monday 1 PM Wednesday 4 PM Thursday 11 AM ...
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### Nonparametric methods for count data?

I have data where the dependent variable are counts of an event. I am modeling the relationship between the dependent and independent variables using a negative binomial model, but I was also hoping ...
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### Discretizing count data (poisson distribution)

Hi I am using next generation sequencing data (Chip-seq) for a machine learning problem. The data is represented as counts of fixed sized regions of genome (in this case 1000 bp) each 1000 bp bin ...
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### Mixed effects model with missing count data

I have bird count data over a period of ten years from 15 different sites. For each site I have the month of the count, the year of the count, and the count number of birds. I need to analyse the data ...
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### How to test repeated, nested, count data

I have samples from an experiment in which I have counted cells. I took 2 pictures of each kidney, photographing both kidneys of each subject. Each individual belongs to a group (infection). My ...