# All Questions

139,125 questions
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### Probability of sparse spectrum

Consider a vector $v$ such that $v \sim \mathrm{Unif}(\mathbb{S}^{d-1})$, the uniform distribution on the unit sphere in $d$ dimensions. Question: is there an upper bound on the probability that $v$ ...
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### Is this a crossover design?

I am working with collaborators who are conducting an education research study to see if there is a difference in learning outcomes between two learning experiences, one with a technology tool (let’s ...
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### What is an appropriate technique for large number of correlated predictor variables with interactions?

I want to allow the effects of a large number of continuous predictor variables to be different depending on which treatment group the individual is a part of. If I had only three continuous ...
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### Longitudinal analysis of incidence rates

I am wondering how to conduct longitudinal analysis of incidence rates. A population was followed 5 years (2001-2005), and in each year "person-years" and "event" were calculated. Now I am ...
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### Approximating Categorical Distribution with Mixture of Normals

I have a categorical distribution, and I would like to approximate it using a mixture of normals. Is there any way to do this simply? I've seen an example on how to use a multivariate normal to do ...
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### Correct calculation of repeated cross-validation classification metrics

We can obtain a resampled estimate of training set classification accuracy from caret::confusionMatrix.train(model) e.g., ...
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### Bootstrap Confidence Bands for Linear Regression (in R)

I am looking for a way to implement non-parametric bootstrap to confidence bands around my regression line for my linear regression model. I am, however, new to bootstrap, therefore I am unsure how to ...
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### Pool redundancy analysis results from multiple imputations of missing data

I have a dataset that includes missing values, and I would like to carry out redundancy analysis using multiple imputation to fill in the missing values. So far, I have successfully created multiple ...
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### Dealing with Endogeneity in a Logit Regression when the Endogenous Regressors are Discrete

I would like to estimate a logit model in the presence of endogeneity. The dependent variable is binary (actually, it is non-binary with multiple ordinal categories, but from what I've read dealing ...
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### Gradient Descent Rule in feedforward ANN

I am having a hard time understanding the Gradient Descent Rule for learning in a feedforward ANN. In particular, how do we determine the initial weight vector, and how is this weight vector adjusted ...
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### Can a ratio of performance be used to measure dependence and assign weights in a weighted average?

With only a modest grasp of inferential stats and maths in general, I've been wondering how one might derive the weights for a weighted average from a variable that isn't as straightforward as a ...
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### Why margins and mfx yield different results in R?

When I run a simple logit regression between a binary variable $y$ over another binary variable $x$, the average marginal effects obtained by the function logitmfx (...
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### Developing an appropriate volatility variable to predict stock returns based on past month

I am doing a project about the predictability of stock returns. I am using following regression model: $$r_{t} = \alpha+\beta X_{t-1}+\epsilon_{t},$$ where $r_{t}$ is the ...
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### Covariance of a square of a normal random variable (X^2) and another normal random variable (Y) [on hold]

Find Cov(X^2,Y) if X and Y are normal random variables with N~(0,1) and Cov(X,Y)=c.
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### Finding interesting subsets of a population - Facet Recommendation

I'm looking for the type of maths/stats to recommend facet selection to users. Let's say I have a dataset eg Person, Language, Age, Income, Suburb (i.e. a combination of numeric, continuous data and ...
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### Derivation of the LSTM Backpropagation equations

From the Coursera Specialization in Deep Learning come the following LSTM backpropagation equations: However, my derivations lead to different conclusions: Please note that in the aforementioned ...
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### How to code effect modifier in a Cox Regression using R?

The definition of the distinction between the effect modifier and interaction term is: Interaction and effect modification are formally defined within the counterfactual framework. Interaction is ...
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### GAM discrete time survival prediction in R

So i've been trying to perform a discrete time survival analysis in R. I have been using the 'discSurv' package to generate the augmented data matrix for the full dataset and performed an stratified ...
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### Interrogating the results of the Markov simulation - Help and feedback highly appreciated

0 I have built a Markov chain with which I can simulate the daily routine of people (activity patterns). Each simulation day is divided into 144-time steps and the person can carry out one of ...
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### Interpreting regression coefficients with cube root transformation of both dependent and independent variables

I have used the cube root $(1/3)$ transformation on both my dependent and one of my independent variables. I would have preferred a log-transformation but my data has both negative values and zeroes. ...
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### Derive signals from a signal vector using a mixing matrix

I am tyring to decompose a noisy vector into a sum of signals. Say we have $s$ independent signals and $c$ channels. Each signal can lead to an increase of output in some, but not all of the channels ...
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### What does the associate editor mean about my sample sizes? [on hold]

The associate editor have a question about my paper. He said "In the Monte Carlo you assume that there are 600 low frequency observations, which seems heroic. What are the sample sizes considered in ...
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### Logistic Mixed-effect Regression: How to have a meaningful fixed intercept parameter?

I have a study where participants view 10 faces and have to guess their first names between 2 options (1 correct/1 wrong). There are 2 between-subjects versions of the faces (the faces are different ...
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### Does the threshold value of a logistic regression hypothesis has an effect on the accuracy?

It is true that the threshold value of a logistic regression hypothesis has an effect on the Precision/Recall metrics. Suppose you have trained a logistic regression classifier which is outputting \$...
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### Comparing hazard function of subset and whole data

Is there a way to compare the hazard function that comes from a stochastic process with the hazard function which comes from a subset of that process? Simulations of a stochastic process generate ...
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### What test to use to compare two proportions (and calculate effect size and confidence interval)?

There are many related questions here and elsewhere, but I found no satisfying answer. There are plenty of related tests and concepts: Z-test, chi-squared test, G-test, McNemar's test, Fisher's exact,...
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### Monte Carlo test for statistical significance of typhoon passage frequency

This question is related to this post: https://stackoverflow.com/q/56288002/6638232 Basically, I am trying to perform a significance test using Monte Carlo simulation but I am having a problem in ...
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### Validity of Weibull distribution

I have come across validation engineers picking the Weibull distribution as a way to generate test stimulus. When they do this, they seem to chose the parameterisation without reference to any ...
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### Coefficient Interpretation when dependent and independent variables are percentages

I have built a linear mixed regression model with fund returns (measured in percentage ie. 0.01 denotes one percent) as the dependent variable. For the independent variables I have percentage level of ...
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### Lars alphas_ results

Could any one explain how the results on alphas_ attribute in Lars model are calculated? In the definition: alphas_ is the maximum covariance (abs value) in each iteration. But when I look into ...
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### How to generate and correlate more than two random variables which are from different distributions given then correlation matrix? [duplicate]

I tried to fit some variables using the non-parametric method(kernel smooth), so those distribution for each variable are different,so cholesky descomposition won´t work for this case. Is there some ...
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### Selection smoothing parameter for using function SPM(library SemiPar)

Suppose i fit a model of the following form: ...