# All Questions

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### Centrality Measures for a directed multigraph

I have a directed multigraph that is used to represent an online discussion forum, where each actor is able to contribute comments to a discussion and have their comments commented on by other actors. ...
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### What is the meaning of regularization path in Lasso or related sparsity problems?

If we select different sparsity levels (i.e. that the $\lambda$ controls), we could obtain different solutions with different sparsity levels. Does it mean the regularization path is how to select the ...
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### Population parameters of a regression

So this has really been bothering me and I was hoping for a (simple!) explanation if possible. Suppose I've specified a linear regression model: Y = beta0 + beta1.X + eps And an alternative: Y = ...
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### Hyper-parameters for pretrain and fine-tuning

When doing deep learning, in particular dnn, it's shown that pre-train each layer in a unsupervised fashion, then fine-tune the weights using the labeled data in a supervised fashion. My problem is, ...
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### How to present the significance of group coefficients from a diff-in-diff design?

How would you present the significance of single group coefficients from a diff-in-diff regression model? t-values and F-values mixed, both in F-values, or using p-values instead?
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### ordered probit model

I have a data set with 7 variables and a One dependent variable.And dependent variable has 4 categories.(not a binormial) so I need to fit a probit model for this.can some one help me.I need codes for ...
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### Examine SVM result by plotting histogram of decision values of training samples

I'm working for object detection(computer vision) and have some problems in SVM training. My training configuration is as below. Balanced training set (positive 3998/ negative 3998) The dimension of ...
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### Hidden Markov Model with conditional observations

I am looking for a research paper that basically describes a hidden markov model that has multiple observations, and some observations that have conditional dependencies. For example, please consider ...
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### Resources for Computational Algorithms

The journal Applied Statistics used to have a section on algorithms, which are available online. Griffiths and Hill also published a selection of these algorithms in a book in 1985. But I can't find ...
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### how to calculate Root Mean Square Error (RMSE) for predicted Probability Density Function (PDF) in Matlab

I have used Mixture Density Networks for probability density function prediction. I am wondering how I can calculate Root Mean Square Error (RMSE) of predicted pdf in MATLAB. Thanks.
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### example of a non-trivial data where leverages would all be equal

i was asked to describe a non-trivial data (n not equal to =/1) example where the leverages would all be equal for QR decomposition question. could someone help?
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### STEP BY STEP approach to learn LDA (Latent Dirchlet Allocation)

I have an urgent need to understand Latent Dirchlet Allocation (LDA) for Topic Modeling. I tried several sources, but it seems I do not have required knowledge to learn this. My statistics knowledge ...
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### Consistency of OLS in presence of deterministic trend

For consistency of OLS estimator for linear model $$y_i = \beta^T x_i + \epsilon_i, \; i = 1,\cdots, n,$$ the model assumptions are usually (the ones I am familiar with) The sequence of random ...
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### What types of statistical analysis technique available to compare two different time series [on hold]

I am currently looking for suggestion to compare or study the two different period time series like sales in 2000 and 2001
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### How should I do a grid search for the gamma in SVM?

I know that you can do a grid search for the C parameter (-c) in libSVM by going through value that go from 10^-5 to 10^5. How should I go about finding the optimal epsilon parameter (-p) ? Is ...
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### multivariate dirichlet for multiple imputation

I dealing with 3 covariates {x1, x2, x3} all three are discrete and contain missing data. ...
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### Distribution comparison across different treatments

if I have a table like this In which, site = different sites of measurement (tissue or organ) type = different types of virus And I want to ask something about the data 1.What test can I use to ...
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### Comparing the distribution (or properties of distributions) of large datasets for practically significant differences

I have several populations with a large n (100,000 - 1M+ samples), which i wish to compare. I know that virtually any statistical test i apply will reject the null hypothesis due to the extreme power ...
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### Why is $R^2$ poor for AR model selection used for forecasting?

There is a related question here, about how to calculate the R-squared on a regression with ARIMA errors. I found the answer quite useful, and hoped for some elaboration, particularly on Rob's closing ...
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### Two stage GMM estimator in Matlab

I am trying to create a simple GMM estimator for the mean of a normally distributed random variable using the first three odd central moments of a normal distribution (all of which should be zero ...
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### Boxplots with lognormally distributed data

Context Environmental data (e.g., pollutant concentrations in water, soil, air) are often lognormally distributed. Even when they are not, we tend to assume that they are (for better or worse). ...
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### Filtering Samples of Unequal Size and Correlating Categorical with Non-Categorical Data

Suppose I have a large number of samples, some of which only contain one observation, and some of which contain up to 12. Each observation can fall into one of four categories per sample. This ...
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### Human movement distribution [on hold]

I need help with the mathematical distributions to use to model user movement (user travel pattern) in a city or a given geographical area. I don't have any data; my question is limited to theoretical ...
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### How to update probabilities where datasets and analysis methods differ

Any help would be appreciated, as I'm not sure how to proceed. I have a dataset with binary data and have been able to fit a logistic regression model to it (presence of disease, for example, as a ...
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### package in R for BMA of a logistic model?

I am trying to perform analysis similar to Gerlach et al. (2002). it involves predicting the posterior probability of a particular binary outcome using the previous 5 observations. I was just ...
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### feature selection for longitudinal data

I have a longitudinal data which looks like this. Number of time points are different for each ID. Y is the binary response variable (take values 0 & 1) and X1-X20 are either continuous or ...
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### Using k-means with other metrics

So I realize this has been asked before: e.g. What are the use cases related to cluster analysis of different distance metrics? but I've found the answers somewhat contradictory to what is suggested ...
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### Growth rate vs. Absolute correlations

Conceptually, what is the reason why the correlation between growth rates of A and B would be different from correlation between actual A and B? Under what circumstances would the growth rate ...
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### What is the intuition behind the independence of $X_2-X_1$ and $X_1+X_2$, $X_i \sim N(0,1)$?

I was hoping someone could propose an argument explaining why the random variables $Y_1=X_2-X_1$ and $Y_2=X_1+X_2$, $X_i$ having the standard normal distribution, are statistically independent. The ...
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### Random Forest - understanding k fold cross validation

I am trying to improve my data science knowledge by solving problems available on the internet. I am currently using the R package randomForest to classify the ...
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### Identify the stationary time series

Identify the stationary time series for which $$\gamma(h) =(-1)^{|h|}+\cos \left(\frac{\pi}{4}h\right)$$ is ACVF. This is a homework problem. Stuck at first level. Please give some hints. Thanks in ...
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### Web Scraping - Tracking ecommerce prices [on hold]

I am currently working on a project that involves tracking the prices of several products in 6 different websites. Has anyone here have experience with this: Given the EAN product code (or even its ...
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### Continuous AR model from a Discrete AR model

I have a model of an $\mathrm{AR}\left(2\right)$ process, thus: $X_n + a_1X_{n-1}+a_2X_{n-2}=Y_n \qquad \mbox{for} \qquad n=0,\pm1,\pm2,\ldots$ and I have the equivalent stochastic differential ...
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### Comparing polynomials

I've got a bunch of data on pop singers' performance on the Hot 100 charts over time, and I'm trying to compare the early part of different artists' careers. For example, I might look compare Miley ...
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### Standard error for expected value [duplicate]

I have a computer simulation from which I get a sample of values of some microscopic quantity $X$, i.e. $\{ x_1,\ldots,x_N \}$. I'm interested in estimating the expected value of $X$, i.e. \$E[ ...
19 views

### Rank Histogram or of precipitation data [on hold]

Given a dataset of lines containing 6 wind forecast values plus 1 observed (actual) value in each like: ...
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### Correlation of likert scales for different questions

Can you correlate 2 Likert scales when the question for each one was different? I have 1 question which asks how concerned someone is about pollution. They rank this on a Likert Scale of 1-5 where 1 ...
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### geepack: parameter estimates change sign depending on correlation structure

I'm working on a dataset with the following variables: ...
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### Holt-Winters and Abnormal termination in LNSRCH

I try to fit data with Holt-Winters function in R. Nevertheless, i am getting the following message: ...
27 views

### Is there a PDF for a generalized non-central chi-squared distribution [duplicate]

Is there a PDF for a distribution defined as a sum of squares of random variables pulled from a family of normal distributions with different standard deviation? Is there a way of analytically ...
17 views

### computing mean and sd of d-prime from mean and sd of hits and false alarms

I'm working on a meta-analysis. Some studies report d', others report accuracy (hits and false alarms). I would like to transform all the data into the same measure, d' (also c). However, for many ...
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### Create age and sexmatched pairs to balance Cox regression further

I analyze ethnic differences in risk of cardiovascular events (CVD) in a cohort study of patients with stable coronary heart disease. I know for several reasons that immigrants should have higher risk ...
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### tease out significance

Say I have search data like this AvgCost QualityScore SearchShare 3.12 6 0.6364 Where AvgCost is a ...
31 views

### Can ayone help me in solving the below Problems of probability distribution?

Patients arrive randomly and independently at a doctor's surgery from 8·0 A.M. at an average rate of one in Five minutes.The waiting room holds 2 persons. What is the probability that the room will be ...
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### Extracting the value of an element from Dataframe in R [migrated]

I am very new to R and trying to extract a specific element from a data frame and compare it with an integer. I had a table saved in text file. I used the following to read the table. ...
30 views

### Bayesian probabilty [migrated]

I need to know how to find the Bayesian probability of two discrete distributions. For example the distributions are given as follows: ...
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### Preparing survey data for analysis

I am preparing a complex survey data for analysis. The survey involved a two-stage stratified cluster sampling. In the first stage, I have 7 strata and 4 sampling units and in the second stage I have ...
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### R: Is it possible to estimate the poisson noise?

I have a dataset of many discrete counts (RNAseq read counts per base), which contain both real signals and background noise. The noise is random, and should be poisson distributed. What I would ...