# All Questions

1answer
52 views

### Illustrating power-law properties with Chinese Restaurant Process (PYP)

I often read that Pitman-Yor Process has power-law properties. Let's say I am interested in modelling English word's distribution (which follows power-law). Using CRP metaphor, words come and get ...
1answer
43 views

### About stepwise regression and correlation

I am trying to fit a model to some observed data with the least squares method. Now, I am at the stage where I have run a stepwise regression (traditional), with Entry level $=0.025$ and Stay level ...
3answers
245 views

### Uniform random variable as sum of two random variables

Taken from Grimmet and Stirzaker: Show that it cannot be the case that $U=X+Y$ where $U$ is uniformly distributed on [0,1] and $X$ and $Y$ are independent and identically distributed. You should not ...
0answers
22 views

### lowess: R (& python-statsmodels) vs MATLAB (& biopython)

There seems to be two different interpretations of what LOWESS really means: one from R (also used by python-statsmodels), and one from MATLAB (also used by biopython), see comparison below. Could ...
1answer
17 views

### estimating the population standard deviation from the sample standard deviation

Is there a way to estimating the population standard deviation, $\sigma$, from the sample standard deviation, $s$, if the size of the finite population is $N$ and the size of the sample is $n$? Is ...
0answers
9 views

### Regression Output from R [on hold]

I'm trying to regress the outcome variable "count number" on its lag and season, where 1,2,3,4 represent spring, summer, autumn and winter, respectively. However, I got some very weird output from R. ...
0answers
8 views

### Synthetic Minority Oversampling with Binary Features in the data

I am planning to use SMOTE or ADASYN for creating synthetic observations for a classification problem as the data is imbalanced. The question is, there are Binary variables in the Feature set, and I ...
2answers
25 views

### Output of Scikit SVM in multiclass classification always gives same label

I am currently using Scikit learn with the following code: ...
0answers
23 views

### Observed vs expected values for a dataset with repeated measures

I am hoping you all may be able to help me select the appropriate statistical analysis for a subset of my data. I have a population of monkeys that consists of 50 individuals in 3 groups. ...
0answers
7 views

### Compute effect size based on simulation using different lists of different length

For my research purpose I wrote a small simulation to compute an empirial p-value based on an input gene list and a reference gene list. The idea is to check for each gene in the input gene list, the ...
0answers
22 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. ...
0answers
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. ...
0answers
34 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 ...
1answer
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: ...
1answer
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): ...
1answer
15 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 ...
0answers
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 ...
0answers
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 = ...
0answers
19 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 ...
1answer
21 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 ...
0answers
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 ...
0answers
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 ...
0answers
7 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 ...
1answer
111 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?
0answers
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 ...
1answer
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 ...
1answer
23 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 ...
1answer
55 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? ...
0answers
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 ...
0answers
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 ...
0answers
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 ...
2answers
48 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: ...
1answer
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 ...
0answers
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 ...
1answer
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?
0answers
14 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 ...
0answers
22 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 ...
2answers
66 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 ...
1answer
30 views

### High leverage Points In Logistic Regression in R

Do You Know Any Good R Package For This Model?
1answer
24 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 ...
0answers
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 ...
0answers
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 ...
1answer
45 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 ...
1answer
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 ...
0answers
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 ...
0answers
14 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 ...
0answers
7 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 ...
0answers
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?
0answers
22 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 ...
0answers
29 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 ...

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