# All Questions

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### A chi-squared test for a matrix of data

Given a observable vector $v=[v_1,v_2,\ldots,v_n]$ and a model $m=[m_1, m_2,\ldots, m_n]$ when $\sum_i v_i=\sum_i m_i$, I can use chi-squared to determine the likelihood that $m$ is a good model for ...
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### Choice based conjoint latent class analysis in R

How can we perform Latent class Analysis for choice based conjoint data, to both segment respondents and determine co-efficients for attributes at the same point of time? I know there is a package ...
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### How can I test for changes in the distribution of categorical data over time?

Each week at my organization, we receive X number of type A messages, Y number of type B messages, Z number of type C messages...etc. I want to be able to test if the distribution of these message ...
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### Using contingency tables for testing multiple dependencies

I know that I can determine the correlation / association / dependency between two variables (X= smoker, and Y=cancer) using chi-squared with a 2x2 contingency table: ...
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### how to analyze the results for this binomial test?

I have established the following hypothesis: The probability of successfully passing the course in this trial is less than 50% (alternative hypothesis) The probability of failing the course in this ...
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### Determining whether a successive instances are conditional or independent

I hope I can appropriately describe the problem. I have an example data set with 610 individuals with made up analogy (it's not really about cars). I want to determine the number of people have x ...
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### Repeated Observations Due to Pairings in Logistic Regression

I have data with repeated observations within a given year. Here's a snippet of the data: ...
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### If $\operatorname{Var}\left(\varepsilon\right) = h\left(X\right) \neq \sigma^2$, what can we know about $\operatorname{Var}\left(\hat{\beta}\right)$?

This question uses the derivations found here. Notation Assume: $Y_i=\beta X_i + \epsilon_i$ for random variables $Y_i$ and $\epsilon_i$ $\operatorname{E}\left(\epsilon_i\,|,X_i\right)=0$ so that ...
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### Linear Probability Model Construction

I am dealing with a questionnaire consisting of 15 questions. I performed a factor analysis to all the questions and it has given three factors each consisting of 5, 7 and 3 numbers of questions ...
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### Gibbs Sampler output: how many Markov chains?

When running a Gibbs sampler (for $n=200$ Iterations) with two full conditionals, I get the output $\mathbf{x} = (x_1^{(n)},x_2^{(n)})_{n =1,...,200}$. So $\mathbf{x}$ is the realizations of a Gibbs ...
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### Undergrad linear regression topic [on hold]

I have to prepare a mulitlinear regression research paper with cross-section data. I thought doing something on the credit ratings of sovereign debt (of one of the Big3 CRAs) or something similar. ...
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### Dissertation-results section [on hold]

hello i am wondering if you could possibly give me some guidance writing up my stats. I have recently had a meeting with a stats profession about my results section, basically her advice was to ...
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### maximum likelihood for count data [on hold]

Can maximum likelihood estimation method of parameter estimation be used in categorical data? I was looking for some examples of it. What other parameter estimation techniques work for this kind of ...
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### optimization - cost function matlab

suppose I have a signal x1 always positive of length N = 1000. % signal x1 x=rand(1,1000); x(x<0)=0.01; I have also other 599 signals x2, x3,...,x600 (they ...
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### How to deal with factors with rare levels in cross-validation?

Suppose in a regression analysis in R, I have a factor type independent variable with 3 levels in my train dataset. But in the test data set that same factor variable has 5 levels. Therefore I can not ...
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### Rotation in PCA and Factor Analysis

I want to know what elements I (Varimax-)rotate if I rotate after PCA and after Factor Analysis. Let’s assume a standardized data vector $X$ of dimension $N \times q$. In PCA, I have the formula: ...
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Say I have a highly biased coin that lands heads with $p_h=0.01$ and tails with $p_t=0.99$, and I flip it $98$ times. The probability of zero heads is ${p_t}^{98} \approx 0.373$. The probability of ...
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### Statistical models for Obesity data

I have a data on obesity status of women in a country. This data is based on across sectional study. Now I want to find the determinants of obesity among the women. Here dependent variable is binary ...
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### Compute the probability that the provided classifier label is correct

A binary SVM classifier provides a label $y_c^{(i)}$ for each $i$-th sample provided. This is not assured to be corresponding to its true label $y^{(i)}$, since the classifier could have computed a ...
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### Difference between Cox Proportional Harzards Model and interval-based logistic model for survival regressions

I have a dataset of timestamped trader transactions (to the second). I want to conduct a survival analysis on the trades where a trade is started at startTime and ...
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### Maximum likelihood method vs. least squares method

What is the main difference between maximum likelihood estimation (MLE) vs. least squares estimaton (LSE) ? Why can't we use MLE for predicting $y$ values in linear regression and vice versa? Any ...
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### Is a logit model with a pseudo-R^2 of less than 0.5 a worse model than a coin toss?

I have recently encountered the remark that if a logit model's pseudo $R^2$ is lower than $0.5$ the result is completely worthless because a coin toss is a better model. Is this interpretation ...
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### Incremental SVD implementation in MATLAB [on hold]

Is there any library/toolbox which has implementation of incremental SVD in MATLAB. I have implemented this paper, it is fast but does not work well. I tried this but in this also error propagates ...
19 views

### Why does the Journal of Statistical Software use The Persistence of Memory as a logo?

I find this to be pretty interesting, does anyone know why this is?
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### Which is better, replacement by mean and replacement by median?

I'm doing a project that involves replacing missing values in a set of data (first time doing this). This is involves using to methods "replacement by mean" and "replacement by median" to fill in the ...
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### Clustering not producing even clusters

I'm using k-means clustering to processes running on machines. Dataset sample : machine name, process m1,java m2,tomcat m1,word m3,excel Build a matrix of ...
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### How to visualise the uncertainty of the classification?

I used SVM to do some classification, and SVM can output some probabilities (likelihood) value measuring how likely each data to be one particular class. For example, Data point 1: 90% (class 1) 5% ...
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### Data stratification for long-tailed distributions

I'm encountering a few problems successfully stratifying a dataset that is long-tailed to the right. In my research, I came across this excellent response: Sampling from a long tailed distribution ...
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### Plotting QDA projections in R

When doing discriminant analysis using LDA or PCA it is straightforward to plot the projections of the data points by using the two strongest factors. This can be done in R by using the x component ...
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### Bootstrap analysis for the estimation of Coefficient of variance of a subset

I wanted to estimate the precision estimated as CV= se/mean of a sampling effort (fishing effort=12 gill-nets) of the mean catches based on fish abundances(CPUEmean). I used in R the function: CV ...
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### Semi-supervised Learning Training

I have got some data partially labelled. Therefore, I would like to apply semi-supervised learning for this dataset. Basically, I trained the Support Vector Machine (SVM) using the data with labels ...
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### Semi supervised classification on multivariate data for outlier detection

I have a large multi dimensional unlabelled dataset of cars (price, mileage, horsepower, ...) for which I want to find outliers. I decided to use the sklearn OneClassSVM to build a decision boundary ...
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### F test in random effects panel regression

I'm using random effects panel regression and I've 3 covariates not statistically significant and I want to test if the three parameters associated with those covariates are jointly equal to 0. Could ...
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### confidence intervals around lines from glmer in lme4

I have spent a large amount of time trying to figure out how to generate a desired plot, and was wondering if any one can help. The plot is to illustrate an interaction between 'time' and 'group' on a ...
18 views

### Studying complex systems (complexity)

Complex socio-technical systems is one my research interests. Since I plan to further study such systems and related phenomena, I've done a bit of reading and ran across various books, such as Bar-Yam ...
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### Graph showing the first stage effect

I am using a 2SLS approach in order to estiamte the effect from increased education. I want to show the effects of the first stage graphically, ie I want to show that the instrument affects schooling ...
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### How to test for interactions of continuous measure with two repeated-measures factors in R?

I am doing an items analysis of difficulty ratings of a large set of math problems which were constructed to represent the factorial combinations of two binary factors, feature1 and feature2. The ...
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### Independence of the products of two independent normal variables with a Rademacher variable [on hold]

Let $X$ and $Y$ be two iid $N(0,1)$ random variables, and let $Z$ be a Rademacher variable i.e. $P(Z=1)=P(Z=-1)=0.5$ distributed independently of $X$ and $Y$. Let $U=XZ$ and $V=YZ$. Are $U$ and $V$ ...
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### Pre-post measurements with a control group

I am running a study looking at the effect of Vitamin C on muscle function. For my study design, I had 2 groups: A treatment (vit C) and a control (no treatment) group. Pre and post measurements were ...
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### 2SLS probit vs LPM

I am using 2SLS to estimate the effect of education on the probability that one works. In the first stage I regress education on my instrument and the other exogenous control variables. The same ...
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### Types of regressions

My aim is to see if there is a pattern between demographic features of my participants and the their chance of employability . The 14 human, social and organizational variables are the key factors for ...
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### Cox MSM or Recurring Event?

I have dataset containing clients' history of active and inactive periods (if there is any) up to present day. Also lots of info as time dependent covariates. I want to model this as MSM, where both ...
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### 'invalid file specification' when running Monte Carlo simulation [migrated]

I programmed the monte carlo simulation down below. The simulation itself works, but I do not seem able to summarize it. When I run my full program, the do file automatically ends after the monte ...
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### Multi-Level (Sparse) A/B Testing

I've been reading some articles about Bayesian A/B testing such as: http://engineering.richrelevance.com/bayesian-ab-tests/ but my application requires a framework for handling sparsity and group ...
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### Using the terms significance, probability or likelihood, in connection with estimators

Imagine a number of variates $x_i$, and a number of processes $P_k$ which depend on these variables, in an unknown way (ie no clear cut formulas to work with). Now consider the scenario where you ...
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### learning if instances from a dataset are part of the same subset

I was wondering if there are some well-known machine learning methodologies for subset learning. In other words, to learn if two instances are part of the same subset or not (boolean label?). One ...
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### How would I find out the number of IP addresses that made a google search in Russian from Thailand? [on hold]

Essentially, I want to get an estimate of the number of Russian speakers living in Thailand. There's also the question of how would one filter out the hotels.. but that's probably much more difficult ...
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### What would be an efficient way of representing a known discrete distribution with a number of samples?

So, say that I have a known discrete probability distribution, for example: [1] [2] [3] [4] [5] 0.08072 0.0642 0.2853 0.3206 0.2492 What I want to ...