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Questions tagged [modeling]

A statistical model is a formalization of relationships between variables in the form of mathematical equations. A statistical model describes how one or more random variables are related to one or more random variables. The model is statistical as the variables are not deterministically but stochastically related.

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Comparing a Z-score from a model fit on real data against a randomized input

I have a quite complex statistical model that fits the parameter $X$ for some input data. The form of this model is irrelevant for the further question (at least I think so). Let's say I provide two ...
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How to deal with values in predictive modeling where missingness is a predictor?

I have been reading about how to deal with missing values in predictive modeling and majority of the suggested solutions deal with either imputation or deletion. But what to do with missing values ...
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Linear regression where some known records have a measurement error in dependent variable

I am modelling data where the dependent variable is the number of units of a certain product sold each month in each area. In all areas, the product is sold by a chain of shops 'A' and we have exact ...
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What is the process for detecting a 0.2 gallon/hour leak in an underground petrol tank with an accuracy of 95% or more?

Current EPA regulation stipulates that SIR (Statistical Inventory Reconciliation) vendors must be able to detect a leak of 0.2 gallons/hour with a probability of 0.95 or higher, and a false alarm rate ...
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Steps of getting the beta-geometric distribution [on hold]

What are the steps to get the formula below which is for the beta-geometric distribution? P(X=k)=u∏k−1i=1(1−u+(i−1)θ)∏ki=1(1+uθ) I'm getting some difficulties in estimating the parameters for this ...
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Which method should I use? Calculate default probabilities

I have a car data, which looks like this: ...
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20 views

Statistical testing in clinical research

I just did a univariate binary logistic regression to classify a disease based on some medical parameters. Now only one variable showed significant result (p-value < 0.05). Assuming sufficient ...
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Tobit versus OLS, is dependent variable censored?

I would like to investigate possible relationships between arbitrage profit of crypto exchanges and exchange's order book characteristics, such as volatility, spread, liquidity. I compute the ...
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Covariance matrix for a 2D state vector

I'm performing Optimal Interpolation (which in fact is a simplified Kalman filter with constant $\mathbf{K}$). My state variable is a 2D concentration field with a size of 370 x 400 on which I try to ...
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Ways to anonymize the data for logistic regression

We are testing a Proof of Concept with an external vendor to whom we need to provide the data in an anonymized way. Apart from removing the client details/identifiers, what are the best ways to ...
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1answer
33 views

Excellent model fit but high VIF

I want to use a predictive model for a time series variable M that is related to an other variable X. I can generate independent scenarios for X and I need to generate corresponding values for M. ...
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Help in understanding notation for NO-GROWTH MODEL (OpenMx)

I´m having a hard time understanding the OpenMx notation from this handbook "Growth Modeling" (Grimm, Ram & Estabrook, 2017). The authors compare the script from MPlus and OpenMx with regard to ...
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Finding most effective sequence of treatments

I am looking for (any) pointers on how to approach the following abstract problem. Not: my statistics background is very limited, so I might very well be missing something obvious. We have subjects ...
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Predicting the minimum score needed to win a contest [closed]

Given a nationwide contest with 1M contestants where the top 10 contestants that have answered the MOST correct answers in a test will be awarded a price. If we know already that at least 100 people ...
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Investigate whether hospital infections tend to have common etiology in the same ward/hospital

I have data from a national prevalence study on healthcare-acquired infections (HAI). I would like to know whether two patients being in the same ward (or in the same hospital) have a higher risk of ...
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27 views

Why does Random Forest not find this simple categorical interaction?

The questions: Why is Random Forest not better at finding an interaction of a simple indicator $\times$ continuous variable? What kind of machine learning model would be better at finding this ...
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Multiclass classification with a balanced dataset and one high-priority label

I have a balanced dataset for a multi-class classification problem with one high-priority label (this ought to be classified properly at all costs). How do I go about creating a workflow for this ...
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2answers
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How to address nonlinearities among covariates when modelling?

Generally, it is recommended to drop one variable from modelling when we found any collinearity among two variables. But what when two or more independent variables have nonlinear relationship. Can ...
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Using a surrogate model for the solution space of an optimization problem

I have an optimization problem: Given a complex $n\times n$ covariance matrix $C$ one must find a complex $n$-vector $v_C^\ast$ which (approximately) minimizes an objective $f_C(v)$ over all space. $...
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How to evaluate o model that predicts probabilities for a game between two players

I have a theoretical question. Let's say we have a game that is based on time (duration T) (something like football or basketball), and two players play each ...
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18 views

Modelling Inverse Gaussian Distribution for Survival Data in R

I am fitting survival data with different distributions in order to determine what best characterises my data. I believe that the inverse gaussian distribution may be a good fit for my data but I have ...
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How to model a time series problem for RNNs?

I have projects as input data, each project has a weekly progress report (hours of work completed in this week). A project can have an arbitrary duration, but let's say it's usually around 100 weeks, ...
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1answer
21 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 ...
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Modeling daily purchase events / website traffic, time series or independent events?

I've been thinking about how best to model sequential events like purchases on a website, or website traffic. I'm curious if people think this is best modeled as a poisson process (or something like ...
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Comparing populations with multiple variables

My datasets represent the sales of a company with the phone calls they made to promote the products (some zones have sales but no phone calls). I also have the total population per zone which I Can ...
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Problem doing Machine Learning in this dataset

I have a problem to obtain good performances with a dataset. I have to predict the flow of visitors in my city given the distance of origin of tourists and the number of inhabitants of their city of ...
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1answer
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Analysing count data for biology

I have twenty observations of three dependent variables and of sixteen independent variables. The dependent variables are: 1) number of species, 2) number of individuals, and 3) index of Shannon. The ...
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Simplest model for simulation of inter-arrival times with long-memory

I'm trying to model the inter-arrival times of stochastic point process that I've observed for the purpose of simulating it. The Autocorrelation Function (ACF) of the inter-arrival times shows ...
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Graph problem with X nodes looking for Y paths with the most similar length. (shortest path / Chinese post man problem)

There is exactly 1 start node and 1 end node. There are also X (in this case 7) nodes, each connected to all other nodes and the start and end node with different lengths of the paths. The visitor ...
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Interpretation of singularities in AICc and adjusted r-square

Wikipedia states the small sample size AIC for an univariate, linear in paramters mode with normal residuals as: $$ AICc=AIC+2\tfrac{k^2+k}{n-k-1}, $$ where $n$ denotes sample size and $k$ the number ...
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Can two variables be included in same model when if binary B=0, continuous C>0 and when B=1, C=0?

I am interested in looking at the effect of both a binary predictor ("B") and a continuous predictor ("C") on an outcome. However, the value of C is conditional on B in that for B=1, C=0; for B=0, C>0....
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35 views

How do I model count data (Poisson regression) that has a seasonal pattern?

I'm rather new to R and poisson regression and have a few questions. I have count data of incidents per month, a couple years prior to an intervention and 1 year after. I want to use poisson ...
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Confidence interval using Monte Carlo procedure for modelled data

In a project, I have to model volumes data using two parameters given by a dataset. I have a global results for it but I need to construct Confidence Interval around the value in order to give ...
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1answer
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How to give more importance to one variable in a logistic regresion model? [closed]

I'm adjusting a logistic regression model for prediction, but if the person interested says: All variables are important for me, but especially X2 is more important. How I give that variable more ...
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Model for semicontinuous data with structural and sampling (true and false) zeros

I am dealing with a very hard-to-work data set: fish larval density. It is a semicontinuous data, with 90% of zeros and a right-skewed distribution, with few very large values. One problem is that ...
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Bivariate vs. multivariate analysis

I have been reading a few papers lately that has done both bivariate and multivariate analysis on their data. What I have seen most of the times is that they usually do the bivariate analysis first, ...
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Comparing the effects of two categorical variables on one dependent variable?

Suppose I have two dummies: program A and program B. I want to see if enrollment in program A has a bigger effect on reading scores than enrollment in program B. These two dummies are not perfectly co-...
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General time series questions

I realized I was doing lots of threads on the same topic so I decided to consolidate my questions here. I have read time series for years (I am not a statistician, I have graduate degrees that ...
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1answer
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Multiple categorical IVs and DVs with 3/5 levels prediction model

I have a data-set with 8 categorical IVs with 2/3 levels (one level for one type of conditions), 2 categorical DVs with 3/5 levels (one level for one type of responses:dis/even/ad). Participants ...
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25 views

Statistical analysis for quasi-experiments

This is my first message on this forum. I hope I am not doing any mistake. I must analyze data obtained after a quasi-experiment and I am not sure how to proceed. The experiment has been carried out ...
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Which model can I use in my regression analysis if I have time series data?

This is my data set I have collected for a 10 year period. My dependent variable is Gini Coefficient and the rest are my independent variables.
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Time-series forecasting of weakly correlated, univariate series

Given an event that happens with a probability of $\lambda_1$, and another event happens with a probability of $\lambda_2$, what is the probability that they both occur? I have a dataset of ...
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Random effect vs. fixed effect with a huge amount of dummies

I am interested in examining inventor features on their inventive performance using patent data. I have an unbalanced panel data of 7000 inventor-year observations on 3000 inventors over 15 years ...
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What to do when ACF and PACF plots of the residuals show significant lags?

I have a binomial glm modelling a proportional RV against a categorical predictor. The formula looks like this ...
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21 views

Poisson Gamma Distribution in R - Creating Enrollment Modeling Curve

I'm trying to create an enrollment curve for a clinical trial based on the following variables: Country start up timelines (staggered), Number of sites, Number of total subjects needed, Number of ...
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Correlation of phrases and answers to them

If I ask question in wrong forum, let me know, I'll delete it. I try find methods, methodology to create predicative model. Namely, I want to investigate the relationship between the sentences and ...
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1answer
40 views

Mixed model - maximum number of groups?

I am trying to fit a mixed model to determine the effect of X on Y after controlling for non-independence in my data. Non-...
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16 views

Bayesian Model Validation in BEST

I am trying to perform BEST using pymc3 for finding difference between 2 groups of values (values from same group before and after). After performing similar analysis as shown in the link, I see no ...
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156 views

How can I compare models without fitting?

Regression and machine learning are used in the natural sciences to test hypotheses, estimate parameters, and make predictions by fitting models to data. However, when I have an a priori model, I don'...
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Pattern between different services

To start with, I have very limited knowledge regarding models / stats. We have few services which are interdependent. Let's say we have 5 services, A, B, C , D and E. We can roughly have a mapping ...