# All Questions

3 views

### Transforming Cross-Sectional Data with Valid Zero Values

Apologies in advance as I'm somewhat of an econometrics novice. I am working with cross sectional data for 48 countries with a continuous dependent variable (total foreign aid received) that contains ...
10 views

### Conditional independence iff joint factorizes

I have proven that: $X⊥Y|Z\ {\rm iff}\ p(x,y|z)=p(x|z)p(y|z)$ for all $x,y,z$ such that $p(z)>0$. The next question is to prove an alternative definition: $X⊥Y|Z$ iff there exist functions $g$ ...
9 views

### Weight of Evidence(WoE)/Information Value(IV) in R

I am building a credit scoring model in R. I have to run logistic regression. But my number of variables is too high, about 3000. I have both continuous and factor variables. And number of observation ...
19 views

### Negative Binomial Distribution R

This question was given in class and I was wondering how to do this in R: "Sixty percent of a large lot of old spark plugs are still usable, and they can be individually tested to determine this. Let ...
2 views

### kFold and defaul gamma in libsvm

I have a 1600x8 value table, trying to do a SVR. After a few validations, c=2048/gamma=2 have the smallest MSE in cross validation. With this parameters, the test part was not good as C=2048, and a ...
2 views

### Adding exogenous input to data (to expand ARMAX)

I am facing the following problems: 1) I am trying to add an exogenous input to an existing ARMAX model. I already identified a good fitting model with small MSE for my system. ...
8 views

### How to find optimal penaltyparameter C for SVM (regression)

I am training an svm regressor using python sklearn.svm.SVR From the example given on the sklearn website, the above line of code defines my svm. ...
19 views

### Confidence interval for a proportion

Let's say I want to built a confidence interval for a proportion. I have seen that many times this is made from the standard error: $1.96\pm SE$ taking SE from $SE=\sqrt{(p(1-p)/n)}$ But I guess ...
13 views

### How do I contrast code for a factor where one level is the application of both of two others?

I have a factor 'Music' that has four levels: none, piano, guitar, and mixed. Subjects gave a response hearing no music, piano only, guitar only, or piano and guitar, so I want to create an lmer model ...
4 views

### CBC analysis using choicemodelr - interpretation of the output attribute values

I finished a choice-based conjoint (CBC) survey. Now i am evaluating my results with the R-Package "ChoiceModelR". With this i get Beta Values, with which i can, for example, compute attribute ...
6 views

### Calculating sample size of a mixed ANOVA in R (2 between, 1 within variable)?

I'm searching for a built-in function in R for calculating the required sample size (given certain power, alpha,..) of a mixed ANOVA (2 between, 1 within variable, 2x2x2 design). Does this function ...
4 views

### density estimate for continuous support with continuous frequency

I have data with continuous frequency and a continuous support which I'd like to analyze and plot using a kernel density estimate in R. I can create the basic plot in JMP fairly easily using the ...
8 views

### Machine Learning Predictors Evaluation Using R

I've bee using R for predicitve analytics and here is issue: I'm trying to predict the species (categorical variables E1, E2, E3 and E4) of an animal using as predictors a set of nominal (NO1, NO2, ...
22 views

### How to interpret PCA on time-series data?

I am trying to understand the use of PCA in a recent journal article titled "Mapping brain activity at scale with cluster computing" Freeman et al., 2014 (free pdf available on the lab website). They ...
27 views

### How to Calculate π In R [on hold]

This GLM From My Data How To Calculate π With R. I Need R Code.
13 views

### Interaction effect of 2x2 ANOVA in meta-analysis

I want to meta-analyze the interaction effect of a 2x2 ANOVA. (I am not talking about an interaction in the meta-regression, as in this question but about an interaction as the focal effect that ...
8 views

### Checking the proportional odds assumption holds in an ordinal logistic regression using polr function

I have used the ‘polr’ function in the MASS package to run an ordinal logistic regression for an ordinal categorical response variable with 15 continuous explanatory variables. I have used the code ...
5 views

### Python “feature_importances” for most important factors

I'm a little unsure as whether this belongs in stackoverflow or cross validated. I have found a few posts on this topic , but I have not found the following question. Is it accurate to run the feature ...
6 views

### Estimating a Poisson process when arrivals occur out of order?

TL;DR: Given a Poisson process with constant intensity $\lambda$, but you are hearing about arrivals out-of-order, how would you (sequentially/iteratively) estimate $\lambda$? What if the problem is ...
20 views

### SVM parameters clarification

James et al. in An introduction to the statistical learning (p. 351) claim that the solution to the support vector classifier problem involves only the inner products of the observations. They ...
15 views

### Perturbation of binned random variables

Setup: Assume that we have an interval coded random variable $T$ which takes values in the set of half-open intervals $\{[L_1, U_1), \ldots, [L_K, U_K]\}$, where $U_k$ and $L_k$ are the upper and ...
28 views

### Regression function of “non-regressible” data

I have some background in probability, and now trying to understand statistics, which sometimes leads to the questions of the following kind. Let $X$ and $Y$ be two random variables that represent the ...
16 views

### Two-point correlation function

I have been using a code that calculates the two-point correlation function xi(r). xi(r) is defined as a measure of the excess ...
23 views

### Does Hoeffding's inequality apply to sampling from finite populations?

Based on Hoeffding's theorem, one could easily find the minimum number of samples required for the inequality $\Pr \left(|\bar{X} - \mathrm{E} [\bar{X}]| \geq t \right) \leq \delta$ to hold as ...
6 views

### Bootstrap glm and extract pvalue

I am running a glm model using bootstrap, I can extract the coefficient mean and the confidence intervals for all the factors in my model. But how can I get the pvalue from there? Model: ...
46 views

### Which mean value should I use

I am to test the transformational shifts in three different directions for 3 different imaging techniques in a group of 30 patients. I am trying to prove one is not statistically different to the gold ...
11 views

### Where can i find publicly available dataset for sentiment analysis? [on hold]

I am searching for a labeled dataset which have reviews and what kind of emotion it generate. ex - ...
15 views

### Effect of combining features on classification

I have 2 string features F1 and F2 based on which I am trying to perform classification. I have two choices, either to use the ...
45 views

### normality testing

What is the best method for testing for normality? I have a smaller data set today (30 in each group) and on the histograms none of them look normally distributed at all, whereas with the skewness ...
17 views

### How to analyse a factor experiment with feature extraction, clustering and classification algorithms as factors?

Currently I am doing my final project, which consists of designing an experiment to test several combinations of algorithms on a dataset, such as feature extraction, clustering, classifiers and ...
10 views

### Quantifying the similarity of distributions

I'm looking to quantify the similarity / difference of two income distribution pairs and then compare the quantity with other distribution pairs. Any pair of distributions have the same number of ...
5 views

### Softmax maximum likelihood problem: arbitrary constant

I'm doing a multiclassification with a softmax function. The probability of a sample $j$ belonging to class $k$ is given by the softmax: ...
42 views

### How to compute confidence bound in linear regression

In a simple linear regression problem, let $A$ be an $m\times n$ matrix of samples, $A=[x^T_1; x^T_2; ...;x^T_m]$, $w$ is the $n\times 1$ parameter vector, and $b$ is $m\times 1$ response vector. The ...
8 views

### Fit stochastic differential equation to data

Could I have some review of the method I used to fit following SDE: dX = f(t) dt + s X dW Fitting method: Calculated sample for sdW from our data as: sdWt = ...
20 views

### Splines and clinical dataset query

Perhaps off topic or not directly suitable for crossvalidated but does anyone know of a good dataset with a clinical aspect I could use to teach myself how to use regression splines (in R)? I always ...
5 views

### Using googleVis api in java [migrated]

I have used googleVis api in R for dynamic map.Now i am trying to make a small webapp in which servlet access this api and the result is displayed in jsp.But i am not able to access googleVis api from ...
44 views

### Is every correlation matrix positive semi-definite?

I am generating correlation matrix by some new algorithm. Generated matrix is non positive semi definite matrix. I'm getting few negative eigenvalues. Rest of eigenvalues are quite equal to ideal ...
94 views

### Can somebody identify this distribution?

I am searching for the name of the distribution associated with this density on $\mathbb{R}_+$: p(r|\lambda) = \frac{2\lambda ...
28 views

### Equivalence testing - tost method - why CI of 90%?

In testing for equivalence via the two one-sided test approach with confidence intervals, a (1–2α) × 100% confidence interval is calculated to check for equivalence. I assume this is because you ...
18 views

### Does a well-fitting model have shallower chi-square minima than a poorly fitting one?

I am trying to fit some data with a range of models with some variable parameters, to determine which of the possible models best describes the data. I have noticed that if the model is a poor fit, ...
7 views

### Autoregressive model - predictive power

I have estimated a VAR (vector autoregressive) model on credit growth in STATA. I want to test its predictive power by comparing its estimated credit growth to observed credit growth (correlation ...
171 views

### Do I need to correct for multiple hypotheses? p-values all go to one

I have two groups, C and A, where C is control. In both groups there are about 3,000 proteins. For each protein we acquire six measurements in both C and A (these are mass spectrometry intensities by ...
4 views

### Determing goodness of fit at data with few and sometimes heavy change

Currently, I happen to analyze data where I do have a data matrix for two time points each. Each of these matrices is of dimension nxm, where n is the number of samples and m is the number of ...
17 views

### Can I use the correlation value to measure the correlation between two variables when observations in each variable have auto-correlation?

I have two variables: urban areas farm areas. My observations are urban areas and farm areas in each year. But these observations are the cumulative ones, so observations in each variable have ...
12 views

### Is it correct or not I applied PERMANOVA-test and interpreted results?

I want to associate nutrients with microbiota bacteria composition. My data consist of two tables: nutrient table (row - patients, column - some of nutrients, e.g. protein, calorage); bacterial ...
10 views

### power of chi squared test for two proportions with gsDesign package in r

I have problem with calculating power for two sided chi squared test for the following design: Study includes 200 patients (100 patients per group). The null hypothesis is that p1=p2=30% and ...
6 views

### how to take the sum in using 3 point scale

I have conducted a survey through a questionnaire which consists of 45 questions grouped under 6 independent variables and apart from this i have taken 3 dependent variables which i want to regress ...
20 views

### Sampling Size for a large Dataset

I am having a dataset of size upwards of 200 million rows. I have no knowledge of the distribution of this dataset. Would like to perform some analysis on this - like look at the ...