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 ...

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Complicated joint distribution with constraints on the ratio

I'm trying to create random draws of pairs of numbers based on desired distributions of the numbers and the ratio of the two numbers. Let me explain in more detail, although I apologize if my notation ...
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9 views

How to calculate the probability of a sample to get a specific pattern, given all samples and features?

I have a data aggregation tool, which collects information on many samples (clusters of molecules in this case). So it can create a sparse matrix of NxM binary values (N answers of 0 or 1 for M ...
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25 views
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9 views

Allocation of product with ANOVA or something else (?) in R - what direction and tests to use?

Assuming a very simplified view of my data looks like this: ...
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1answer
20 views

Statistical Modeling with the combination of two models

I'm having a modeling problem now. Assume we have discrete random variable Y and continuous random variables X and Z. First, we assume a logistic regression between Y and Z.(Assumption One) Also, we ...
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29 views

About the appropriate regression model

I have a quantitative dependent variable and all my explanatory variables are qualitative (binary or multi-category). I need to analyze the impact of each level on the dependent variable. I also need ...
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34 views

Which estimation technique should I use?

I have time series of six variables from 1973 to 2012, where poverty head count ratio (HCR) is taken as dependent variable. Consumer price index, GDP growth rate, population growth rate, revenue ...
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38 views

Regression multiple customers per month

I have a file with sales for one complete year. Multiple customers, month number and total sales (per customer): ...
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34 views

Is my Sales growth dependent on Commissions/Discounts and how do I analyze this in R?

We are capturing sales data by time series (Month by month). Some of the items have commissions and some have discounts and others have both commissions and discounts. Is it commissions or discounts ...
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6 views

Seasonality in Modeling Population

To conquer the effect of seasonality in data, it is recommended to take multiple sample windows, with each having equal performance window. Question - Should we discard seasonality faced sample ...
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14 views

Smearing estimate for cubic root transform in linear regression

I am building a cost model with cubic root transformation of the cost. Hence dependent variable is (cost)^(1/3). Now, am at a stage where i need to re-transform the predicted value to the actual cost. ...
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15 views

Number of candidate inputs that can be handled by different modelling techniques

Am I correct if I say that some modelling techniques can handle better a larger number of candidate inputs? (If we hold the number of observation constant). Let's say I put around 60 different ...
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1answer
22 views

Best way to combine information from different models

I have 3 models using different methods for the same outcome and predictor variables of a training set. I can apply these models to a new test dataset for predicting outcome variable. Is it a good ...
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22 views

In a EI RxC model, how can I incorporate additional external information?

I'm fitting an ecological inference RxC model, such as described by the Rosen et al. (2001) paper and implemented by the EI R package. I'm estimating voice transfer from the first round to the second ...
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2answers
315 views

How can the “anti-correlation” between these two curves be shown?

I'm looking at data defined on a given feature with respect to two measures. Whilst both measures are defined on the same domain, both measures are defined on different ranges, so, with a view to ...
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5 views

How do I account for non-independence in occupancy modeling?

I have conducted a survey to look at why badgers are visiting some gardens but not others. I have data on badger presence / absence and garden features that might influence badger presence in that ...
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2answers
72 views

Model Selection in Statistics

I have been told not to look at significance level, or not to use forward/backward selection using BIC/AIC for model selection. Let's say, I have 100 survey data with 11 variables and I want to see ...
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17 views

Poisson Regression - missing data, imputation, distribution of fitted values

I'm working on a school project concerning Poisson regresion. I'm trying to build a model for number of cars in household base on American Community Survey. Among explanatory variables are value of ...
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3answers
52 views

Question regarding form of a cost function while training a model

I am beginner in Machine Learning and I am very interested in modelling, simulation and all this jazz :) One of the basic idea I learned so far is the use Cost Function and its minimization in order ...
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9answers
2k views

Are we exaggerating importance of model assumption and evaluation in an era when analyses are often carried out by laymen

Bottom line, the more I learn about statistics, the less I trust published papers in my field; I simply believe that researchers are not doing their statistics well enough. I'm a layman, so to ...
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3answers
71 views

What kind of statistical test is appropriate for this?

Variable X designates a group label (group 1, group 2, etc). Each group represents an amount of time spent watching TV. For example group 1 might watch TV less than an hour a week, group 2 watches 1-2 ...
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17 views

what method for regression on pourcent

I would like to predict/model a repartition between 3 classes (A,B,C). I have a pool of person, and for each pool I have a repartition : A+B+C = 100% this could be my dataset : ...
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35 views

I keep getting the error “iteration limit reached” when using LME

I'm trying to model the effect of island size and island isolation on species richness using a LME. However I'm getting this error message "iteration limit reached". ...
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12 views

Which model approach for data with timings and signals

I have a data set of times, signals and their values. The signals have values from A1 to A6. The first 25 data points of the record are as follows: ...
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7 views

Characteristic Analysis : Variable Stability

What is the calculation of "Score Points" in characteristics analysis report (model stability analysis)? Is it the average of predicted probability falling in a particular variable cohort?
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21 views

Have I interpreted the effect of a confounding variable correctly?

I'm interested in whether feeding rate differ between two species of birds, Species A and Species B. However, tide also affects their feeding rate, and so tide is a confounding variable. In the plot ...
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1answer
43 views

How to treat variable in logistic regression?

I have a variable I do not know how I should handle my logistic regression. The variable is the number of registered students each semester. If I plot it against my binary outcome, I get the following ...
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3answers
209 views

How does linear regression use the normal distribution?

In linear regression, each predicted value is assumed to have been picked from a normal distribution of possible values. See below. But why is each predicted value assumed to have come from a normal ...
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2answers
104 views

Back-testing or cross-validating when the model-building process was interactive

I have some predictive models whose performance I would like to back-test (i.e., take my dataset, "rewind" it to a previous point in time, and see how the model would have performed prospectively). ...
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9 views

Local Sensitivity Analysis

I am tring to have a comprehensive idea about sensitivity analysis. I found numerous papers, books, and serves about global senstivity analysis methods. Coming to the local sensitivtiy Methods, I try ...
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1answer
33 views

Models for fat tails

I am trying to model stock returns and I thought it would be interesting to make a comparison between some well-known models. Could anyone name some well-known models that are used in the presence of ...
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0answers
17 views

modelling a data-set using copula

I have a data set and I transform the data set in to matrix within range [0,1]. https://drive.google.com/file/d/0B6wp1DiHTjBBOXJoc1JhRG5VSHM/view?usp=sharing Can anyone explain the steps in ...
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0answers
36 views

How to make use of less data of a particular class for better modeling?

I have a dataset, say 9000 rows, with some features. Around 8000 belong to class 1 and 1000 to class 0. So, if I am creating a model with any method say SVM, LR, Random forest the model has a tendency ...
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1answer
24 views

Implication of peculiar data set

I've got a dataset which has exactly the same values for the regressors for two of the eight geographical regions but different values for the response variable. What implication does it have on a ...
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1answer
64 views

Mixed models: wrong random intercepts and interpretation issues

I have a dataset of individuals that participated in several races, but not all individuals did every race. Of every individual I have their average speed. My goal is to have a measure of how ...
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19 views

How to model the following dependent variable? [closed]

If I got a dataset which the (count data) dependent variable has the following distribution, how should I model it? I am aware of the zero inflated model and the negative binomial model, but are ...
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12 views

Principled way of collapsing categorical variables with many categories

What techniques could I use to optimize the collapsing of many categories to a few, for the purpose of using them as an input to a statistical model? Consider a variable like college student major. ...
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29 views

Mathematical modeling basics

I have devised an equation for depicting the online activity of users. I shall not be able to disclose the equation here, but it basically is the sum of the weighted means of each activity (activity ...
2
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0answers
60 views

What methods can I use to aid in modeling a smaller data set when I have a significantly larger data set with fewer variables?

I currently have a data set with about 4,000 rows. The current model I have established for it is not very good, and I am going to receive more data for about 150 of these points, and I'm hoping that ...
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17 views

R model formulae

In case of R model building, one should almost always use formulae, but these are not wholly clear for me. Could anyone recommend me a good summary or tutorial? Besides, I have a concrete question: ...
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28 views

Setting Rolling Performance Window

I am in the process of developing a predictive model. I need your help understanding rolling performance window. The objective of the model is to identify customer attrition in retail segment. ...
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0answers
11 views

How can one incorporate prior knowledge about the distribution to which a feature conforms into a machine learning model to improve its performance?

For example, if I were building an SVM to predict whether or not a person is a professional basketball player, and I knew that height (one of the features available) were normally distributed, how ...
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20 views

Bayesian process with noise?

Does anyone know of any research considering Dirichlet processes (or other Bayesian nonparametric models), where sample points have a known gaussian noise attached to their input? I.e. I have a set ...
4
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0answers
78 views

Are all models useless? Is any exact model possible — or useful?

This question has been festering in my mind for over a month. The February 2015 issue of Amstat News contains an article by Berkeley Professor Mark van der Laan that scolds people for using inexact ...
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12 views

how to interprete the ACF/PACF plots? [duplicate]

what the result suggests of the order of the ARMA model?
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10 views

Need some help on discrete valued time series forecasting?

I have data on reservation requests for hotels (your booking information:searching date, check-in, check-out, # of rooms and etc. on hotel booking websites) and am trying to do some analysis on one ...
4
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1answer
143 views

Different shapes of an ROC curve

What are the possible shapes of an ROC curve? Is it necessary for an ROC curve to be shaped like a normal distribution curve? Can we regard the following two curves as ROC with the area under the ...
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16 views

Generating markovian paths

given a 4 by 4 transition matrix P, I want to simulate m Markovian paths of length n I created this function can anyone tell me if this is is correct ? ...
2
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1answer
52 views

Statistical models for Obesity data

I have a data on obesity status of women in a country. This data is based on across sectional study. Now I want to find the determinants of obesity among the women. Here dependent variable is binary ...
3
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1answer
44 views

Studying complex systems (complexity)

Complex socio-technical systems is one my research interests. Since I plan to further study such systems and related phenomena, I've done a bit of reading and ran across various books, such as Bar-Yam ...