# All Questions

19 views

### After Clustering, how can I evaluate which features had the biggest impact?

I've just performed unsupervised clustering (using DBScan) on a dataset for which I have no expert knowledge on. I'm interested in working out which features had the greatest impact on my clustering. ...
22 views

### Ranking Data with % Scores Only

I have some data I need to give an overall 'rank' to and am wondering how I go about this. I have a list of business schools where each has been scored by % for the number of females in 1. Faculty 2. ...
26 views

### Unrealistically high significance when marginalizing over large number of parameters

The setup I've tried to reduce the problem to a self-contained subset for this question, but it still ended up being pretty long. Sorry about that! I have a set of observations of a set of objects ...
26 views

### Selecting variables using SAS and R - all effects are significant even when shuffling the data

Dear all: I need to test which effects I should include in my model for genetic evaluation of cows. I was using the following code in R: ...
17 views

### Full effects from Poisson GLM

I am running a Poisson GLM with count data as response variable and both continuous and categorical variables as predictors. I made use of the following (dispersion is OK): ...
14 views

### identify nature of missingness for categorical variables

could you please give me some hints for identifying the nature of missingness for categorical variables' missing value? I mean, I gave a fast search on google scholar but I didn't find anything ...
16 views

### repeated measures ranking data

I have a repeated measures design where 180 participants rank their preferences for 12 items at time1, and then undergo an intervention, and then they rank their preferences for the same 12 items ...
22 views

### Sampling from a multivariate distribution

Given $X = [X_1 X_2 \ldots X_n]^{\top}$ is a vector of independent bernoulli random variables and $A \in \{0, 1\}^{m \times n}$ is an arbitrary boolean matrix. Define a random variable $Y$ as Y = ...
15 views

### How do I find corresponding clusters in independent samples?

Lets suppose you believe that observations in your data come from K natural but not directly observable categories and you wish to identify these categories with minimal prior assumptions, so you find ...
18 views

### Study Length Over-Estimating Hazard Ratio?

Are cox model studies over too long a time-scale at risk of over estimating (or under estimating) a covariate's effect on hazard? I'm studying inbreeding in a captive animal population. Some ...
14 views

### Excluding Outliers and Influential Observations ($R^2$ and AIC/BIC)

I am working on a cross-sectional data set relating mortgage payments to debt-income ratios. I have some extreme outliers and experimented with excluding them from the model (some 30 observations of a ...
5 views

### How to interpret results. Pre-post survey. Post-only IV, pre and post scores as DV

We are working with an organization that has recently gone through a merger. We did a survey of the entire organization immediately after the merger, and another survey one year later. Our hypotheses ...
6 views

### Canonical correlations for categorical (binary) variables

I have a data set with all categorical variables (most binary). Some variables code social factors, others code mental health issues, a third group code degrees of support from various sources ...
104 views

### Does the Mann-Whitney U-test require the groups to have the same distribution?

If one of my data sets is normally distributed and the other is not, can I do a Mann-Whitney U-test on them, or would they both have to be non-normal?
25 views

### estimating the upper bound on a uniform distribution from max order statistic

I have a question. Suppose that $X_1,\ldots,X_n$ are iid $U(0,\lambda)$ and let $X(n)$ denote the nth order statistic. Suppose $\lambda$ is unknown and should be estimated from the sample. Take ...
31 views

### Machine learning algorithm to predict next user's destination

I'm searching for a way to formulate my problem as a machine learning problem. Suppose I have a history of user's locations, and I want to predict his next location, similar to how Google Now does it ...
18 views

### Fitting a mixture model to spatially correlated data

When the data are spatially correlated, is the usual GMM likelihood function overweighted? The data. Scattering experiment, sensor is like a CCD. Can't see individual events, only density estimate ...
51 views

### Why does a goodness of fit test use the chi square distribution rather than the hypothesised distribution?

This is a homework(-like) question. I know the answer but don't understand it. If we were to answer the question "Are 5 different groups of mammals equally common?", what test would you perform? ...
20 views

### Mean of an interval censored random variable

It is likely that I am incorrect terminology here, but I am trying to compute a "mean" of an interval censored random variable. Here is an example where: 1. a random sample from the standard normal ...
29 views

### What is the limiting distribution of the sample mean?

My question is relatively simple: what is the limiting distribution of the sample mean? But there are some technicalities I want to discuss. context: I was asked this problem in an exam, and I feel ...
17 views

### One Step Ahead Forecasts Using Predict() in R

I just fit a model to a time series. I am now required to generate a 10-year extrapolation forecast of my model. My model includes a time term, a time^2 term, 12 seasonal dummies, and 4 lagged ...
44 views

### Reproduce Cross Correlation results in Python

I'm trying and failing to reproduce the results found in this paper, where the cross correlation between two distributions is calculated: ...
11 views

### What is the difference between R hat and psrf?

In convergence diagnosis in WinBUGS/JAGS/Stan, there are different statistics reported for each variable. In WinBUGS/Stan, Rhat ($\hat{R}$) is reported. In JAGS with the ...
4 views

### Is there a way to get the p-values/standard errors via a function in scikit learn?

Can't seem to figure this out very easily. I am looking for a similar output as that of statsmodels; however, statsmodels doesn't support some of the regressions that I want to do. I basically want ...
10 views

### Why do two identical feature vectors (distance score 0) get different labels in DBSCAN?

I have two identical feature vectors. They have a distance score of 0. I perform DBSCAN Clustering (using sci-kit) and they get different labels. Is this expected behaviour?
13 views

### Is 0 mean of residuals assumption crucial for every model?

I am writing a seminar paper about sales forecasting. I am doing couple of models and I am choosing which one gives the best forecasts (Decomposition method, SARIMA, Brown Exponential Smoothing, Holt ...
21 views

### Testing the equality of two proportions [on hold]

An undergraduate research project involves a beetle that lays an egg on a bean. After several days, a new adult beetle chews its way out of the bean. Sometimes, it does not work and no adult beetle ...
46 views

### Backward feature selection with CV model selection

I am thinking about doing the following to a data set with $N$ samples and $m$ features 1) Train using semi-supervised learning and cross validate on labeled data using LOO-CV to select the best ...
27 views

### High leverage Points In Logistic Regression in R

Do You Know Any Good R Package For This Model?
22 views

### Survival analysis with competing risks

I am analysing the effect of an intervention to reduce length of hospital stay (LOHS) after surgery. The main outcome is LOHS and the intervention is the main exposure. Death while in hospital is an ...
24 views

### Using quadratic programming to fit a piecewise linear model plus seasonality

I am reading this paper on fitting an L1TF model to data using quadratic programming. Section 7.4 states how one could add seasonality to the model however it doesn't go very far into it. I am trying ...
15 views

### The best way for clustering an adjacency matrix

I've had a hard time interpreting resulting clusters of an adjacency matrix. I have 200 relatively big matrices representing subjects that contains partial correlations (z scores) of time series ...
37 views

### Comparison of predictive models

I am trying to compare the predictive ability of various models in predicting survival in patients. I would like to examine the predictive performance of each model using 4 tests: squared Pearson ...
64 views

### t test with log transformation

One of my variables to be compared in a t-test is normally distributed, while the other is non-normally distributed. What test should I use? I thought I should do a reflect log10 transformation on the ...
16 views

### Item Information Distorting Scale

I'm refining a psychometric questionnaire and working to estimate (2PL) IRT parameters for the items in order to score the items. It's a small scale consisting of 5 questions. The MAP and VSS-1 ...
13 views

### PANEL model (MCMC): Equivalent of system GMM in MCMC

I want to fit a PANEL model via MCMC. I am concerned, that I got some covariates that are endogenous. I use MCMC for various reasons, particularly cause I got some spatial dependencies in my model. I ...
6 views

### Need help with Random Effect specification in Multilevel (mixed models): nested Random Effects and a_priori known regimes (MCMCglmm)

I need some advices with the specification of the Random Effects in my Mixed model. I got Panel data from 500 (i) district nested in 50 (j) towns over 10 (t) years. There are 3 ex-ante known regimes ...
6 views

### how to determine whether the results in anova is significant or not by seeing the Critical difference and Sem value?

How to determine whether the results in 3 factor anova is significant or not by seeing the Critical difference(CD) and Sem value?
21 views

### Explain: Latent Variable (e.g for Latent Dirichlet Allocation)

I am trying to understand the Latent Dirichlet Allocation but therefore I need the basic understanding about what exactly a latent variable is in that sense. I know that the basic idea of a latent ...
26 views

### Meta-analyses for variance rather than means

What are the main complications / differences when conducting a meta-analyses where the metric of focus is not effect size (i.e., means) per se, but instead estimates of variances from models? Nods ...
33 views

### Is There A Machine Learning Algorithm For Textual Data With Thousands Of Classifiers?

I've been asked to migrate this from StackOverflow to CrossValidated. I have a problem that I think Machine Learning can solve but am having a very hard time determining which ML Algorithm to use and ...
16 views

### Regression Analysis with String values in column of DataFrame

I have a dataset which is having multiple columns where some column has string values with comma seperated ...
57 views

### Can Chebyshev inequality be used to bound the error of the sample mean?

Can the probability of error of the sample mean, i.e., $\Pr(|\bar{X}-E[X]| \geq \epsilon)$, be bounded using Chebyshev inequality (or something similar)? $X$ is a discrete random variable with an ...
12 views

### As a rule of thumb, difference in amount of administered items: classically scored vs adaptive (irt-based) tests?

I am thinking of developing a new adaptive test. One of the main goals is to shorten existing, classically scored tests. Is there a rule of thumb about how many items are needed to administered ...
9 views

### LSTM implementation using theano

I am using theano scan function for implementing LSTM(long short term memory), but I got error like ...
15 views

### Sound waves are they amplitude or frequency modulated? [on hold]

This question has two perspective one for sound generated by humans and other generated by electrical speakers. From my guessing when we speak we alter both amplitude and to some extent frequency but ...
30 views

### How many features can we use to avoid overfitting the classification?

We have a classification problem: classify type A tumour from type B tumour. In total we have 50 patient cases (25 A and 25 B cases). We use texture or shape analysis to generate features we can ...
42 views

### Compare differences in dependent frequencies

I would like to compare two error rates (proportion of incorrect answers in questions with dichotomous response-format) for two different items, and I am looking for some advice on how to do that. ...