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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35 views

How to compare count of two groups?

I have a two groups of data - 1/ All data and 2/ Selected_season, which is only some subgroup of all data. I want to find out: a/ if proportion of BM, HB, etc. groups is the same in All data and ...
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2answers
45 views

How to do smoothing of data with low counts?

We are a facing a problem of fluctuating shares for each week for the products we are studying due to low counts. e.g. If we have 4 products and for each one we have say like 5,8,3,6 details and we ...
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62 views

How to model a count dependent variable with upper limitation

I have a dependent variable, which have 0, 1, 2, or 3 for its value. I asked participants to choose three items and coded 1 if it is in a certain category and 0 otherwise. I add the three binary ...
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1answer
42 views

ANOVA and Count/Percent Data

I'm just starting to work with some count data and I'm still trying to understand some of the complexities of it, so any help would be greatly appreciated. First the simple version, and then the ...
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30 views

Statitical test on count data

I have a questions regarding a statistical analysis of a biologic experiment. In the experiment I have collected imaging data on the duration of contacts between immune cells. We have compared two ...
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2answers
53 views

Best distribution to handle a ratio of counts as a response variable

A quick statistics question (apologies for the added biology): I have two sets of counts (for the expression of two different isoforms of a particular gene), and to generate the response variable in ...
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25 views

Detecting a significant change in the difference between two rates from T1 to T2

I asked this previously but I failed to activate my account so I was not able to respond to comments and my question was never answered. Here is attempt 2: I have two rates of compliance for two ...
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0answers
14 views

are the percentage differences significantly different from oneanother?

morning, say i have 5 wheat varieties undergoing 2 treatment. when counting the seeds of the replicates the percentage difference between the means of the 2 treatments is 10% for variety 1, 30% for 2, ...
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14 views

Comparing transaction counts between samples

I have a treatment group and two control groups for customers and the count of their transactions: ...
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1answer
48 views

Categorical variable as response in poisson regression

I have data on damages on flowers from different treatments. The damage was originally count data (number of damages per flower) but the person collecting the data categorized the data in four levels ...
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47 views

does the equivalence of Poisson and conditional logit models hold for fixed effect panel data and negative binomial models?

Guimaraes et al. (Rev Econ Stat, 2003, 85/1) describe the conditions under which the results from poisson regression models and conditional logit models are equivalent. I am trying to find out whether ...
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12 views

How to model occurrence counts in groups with latent membership?

I have a dataset that describes the daily history of occurrences of a certain phenomenon P among a certain population. (These are subdivided into certain classes or forms that the phenomenon can take: ...
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51 views

Count data correlation

My dataset is basically a time series - each case is a one day and several events are being observed for each case. I am not experienced in time series analysis but I still would like to get at least ...
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1answer
40 views

Is the Durbin-Watson test appropriate for count data

In determining if there is any serial correlation in a time series of count data, is the Durbin-Watson statistic or similar approaches appropriate? I ask this question because the dwtest implemented ...
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24 views

Modeling Counts With Small Observations

I am new to Cross Validated SE so I am going to try and formulate my question to the best of my ability. I have a large data set that contains $5$ different fields. The fields are ...
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0answers
39 views

10% dip in February for metrics that count?

February usually has 28 days, unlike it's neighbors January and March which have 31. It seems that most countable things will exhibit, on average, a 10% dip in February for the missing 3 days. This ...
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1answer
60 views

Should a Poisson regression be carried out with only 3 data points?

I'm trying to test the relationship between the number of adults counted and the percentage heather cover over 3 areas. The data looks like this: ...
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1answer
139 views

Is it possible to statistically test relationships between counts and percentages?

I have counted adult butterfly numbers over 3 areas and would like to compare these counts with the percentage heather cover on each of the 3 areas. Is this possible? My data looks like this (the ...
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132 views

Estimating abundance using non-normal count data

I have sample counts of $n=20$ or $n=7$ taken from right-skewed and zero-inflated populations. The challenge in each case is to use the sample to estimate the total count in that population. Each of ...
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42 views

Can Principal Component analyses be applied to a counting trait?

I am analyzing a segregating population of plants coming from an hybridization process. The experiment consists in several field plots (according to an augmented design). In each plot a segregating ...
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1answer
52 views

What is a good way of testing for a relationship between two count variables?

I have counts of occurrences of two types of words (A and B) in several texts. What I would like to test is whether the frequencies of occurrence of both types of words across texts is 'correlated'. ...
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46 views

Nonparametric test for largely skewed count data

My research design looks as follows: an experimental game with 4 participants (human subjects), repeated for 20 rounds. During each round, participants are allowed to form bilateral coalitions which ...
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0answers
51 views

Poisson regression on the means of count data

I just finished a small research project about hummingbirds and the effect of hummingbird feeders. I am a bit unsure about how to proceed with the statistics. We placed 15 points in a distance ...
2
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1answer
30 views

Regression when the value of one independent variable is dependent on another independent variable

I need to predict the number of retweeets a tweet receives as a function of (1) whether there is a hyperlink within the tweet's text and (2) the position of the hyperlink within the tweet. If a tweet ...
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2answers
52 views

Predicting zeros with count data model

I'm working with count data (ticket sales, to be specific) and I'm having trouble fitting a model to it. I've tried a linear one and a transformed linear one, but the residuals end up being non-normal ...
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35 views

is Julian day a count data or a continous data

A stupid question but has confused me. My dataframe looks like this: ...
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1answer
42 views

Scaling count data by population size and area

Let's say I want to count the number of people in 10 different counties that have $x$ characteristic. As each of the 10 counties have different population sizes and areas, I want to scale the count ...
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8 views

Modelling biases in selection of one choice from many using count data

In a biological experiment I draw somewhere between 100k and several million datapoints, where each datapoint is one of 1024 DNA sequences. If each sequence has an equal probability of coming up, I ...
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1answer
20 views

I got a good OLS fit for integer variables, do I still need to use count data methods?

First of all, I'm not a statistician, but I'm teaching myself some methods I require for a project I'm doing now. I have a 2D dataset of N observations. For the ith observation, the first entry is ...
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37 views

Mixing distributions to model parameter errors in Poisson

I'm trying to fit a complex model to count data from a detector. I have background and background+signal data. My goal is to obtain information from the signal by fitting a Poisson with $\lambda = ...
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1answer
67 views

Count data model validation

I'm using different models to model count data, the purpose of modelling is prediction. Values vary from 0 to 7. I try to use cross-validation method to assess out-of-sample predictive perfomance, but ...
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0answers
20 views

Using Resampling to understand a large table

I have a data set that is very large. The attributes (columns) are several thousand. Some are sparse others are not. Some are ordinal, others interval, nominal or ratio. The row size is 10s of ...
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45 views

Evaluate deviation from negative binomial model

I'm trying to figure out how to determine to what extent a sample deviates from a negative binomial model fitted to a larger population. As an example, I generated counts of doctor visits for a ...
2
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0answers
158 views

Standardizing count variables in panel data with overdispersion - R or Stata

I'm running a regression where the dependent (response) variable is a highly dispersed (slightly zero-inflated) count and the explanatory (independent or predictor) variables are continuous, counts as ...
2
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1answer
131 views

GLM for count data

I ran an experiment with an eye tracker and my data frame has this look: ...
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84 views

Back Transforming Rates in Poisson GLM with Box and Cox Transformation

Suppose I have fitted a Poisson GLM to model rates as follows: > fit.1=glm(response~X1+X2+ offset(log(population)),family=poisson,data=...) I can get the ...
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1answer
118 views

Data transformation for count data with many zeros

I have a count dataset that contains many zeros and a discrete variable that contains many zeros as well. I would like to see graphically which kind of correlation exists between these two variables. ...
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1answer
58 views

Correlations in count data

I have two count data variables X and Y that contain many zero values (90% in X, 60% in Y). I would like to check if a correlation exists between these variables, but I'm not sure how to proceed due ...
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29 views

Confidence interval for fit to poisson count data, for beginner

I have the following graph, which I then normalise and attempt to fit to. The data is a histogram of counts at a given time. The fit then looks like: The issue is that the parameters ...
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25 views

Showing count data can be dichotomized without losing too much information

I am working with a set of data that has accident counts by year from taxi drivers. R code: no.accident <- c(16003,2355,4433,18823) one.accident <- c(172, 26, 232, 9) ...
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115 views

Error bar for Poisson count data

I have a set of data, counts versus time. The whole data looks like this Here is a sample ...
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103 views

How to guess a curve distribution from count data

I have a sample composed by 2500 count data values. I've plotted in R the corresponding histogram and ecdf. I've run the One-Sample Kolmogorov-Smirnov test to check if the distribution is either ...
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29 views

Additive Index: Count data or multinomial?

I would like to use an additive index, validated by Mokken analysis, as a dependent variable in a logistic regression model for categorical dependent variables. The index consists of adding values ...
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96 views

Non-parametric estimators for time-varying binomial proportion

I have a bunch of count data associated with time intervals (potentially overlapping and of variable lengths), say $(s_i, t_i, n_i, N_i)$ where $N_i$ is a count of the total number of events ...
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1answer
47 views

Interpretation of Count Models Based on Weibull Interarrival Times?

This question is an extension of this question, but more specific. This paper E. Bradlow et al is a Weibull counting model which I am using to estimate how many failures will happen between ...
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1answer
82 views

Fitting Mixture Distribution of Poisson and Negative Binomial (Delaporte Distribution)

I am trying to fit a model to some simulated data. The idea is to use ML-Estimation. However, I am totally lost. I have a dependent variable which is a sum of two (unknown) variables. The first part ...
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47 views

Exp(B) value outside 95% Wald Confidence Interval

I ran a negative binomial regression on some count data using SPSS. The intercept had an Exp(B) value below the lower limit of the 95% Wald Confidence Interval. I've never seen this happen before ...
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252 views

Regression model for proportion or count when counts of outcome and total events are often zero

I need help thinking about and identifying the kind of regression analysis that would be appropriate for this problem. Nothing I've discovered so far seems quite right. Referrals to articles or ...
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0answers
138 views

Suitable method for modelling (underdispersed?) count data with lots of zeros and long tail

I have a small data set of counts of bees. I tried a simple Poisson model without random effects but it was very overdispersed (3.95). When I fit a GLMM with random effects (using glmer in lme4) it ...
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380 views

Trouble finding good model fit for count data with mixed effects - ZINB or something else?

I have a very small data set on solitary bee abundance that I am having trouble analysing. It’s count data, and almost all the counts are in one treatment with most of the zeroes in the other ...