# All Questions

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56 views

### Build statistical model

I need to build model where y depends on x (y~x). But while I have the usual data for Y, I only have a range of values for X, e.g. ...
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98 views

### Multilevel modeling of experimental data with repeated measures in the same condition of factorial experiment

I'm struggling with modeling some experimental data using the lme4 package in R, and would appreciate input. My experimental design is as follows: subjects ...
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43 views

### Simple question about notation

In the context of likelihood-based inference, I've seen some notation concerning the parameter(s) of interest which I've found a little confusing. For example, notation such as $p_{\theta}(x)$ and ...
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57 views

### Bayesian analysis with histogram prior. Why draw simulations from the posterior?

This is a beginner’s question on an exercise in Jim Albert’s “Bayesian Computation with R”. Note that while this might be homework, in my case it is not, as I am learning Bayesian methods in R because ...
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36 views

### Link Anomaly Detection in Temporal Network

I came across this paper that uses link anomaly detection to predict trending topics, and I found it incredibly intriguing: The paper is "Discovering Emerging Topics in Social Streams via Link Anomaly ...
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46 views

### Visualizing results from multiple latent class models

I am using latent class analysis to cluster a sample of observations based on a set of binary variables. I am using R and the package poLCA. In LCA, you must specify the number of clusters you want to ...
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40 views

### Likelihood analysis for exponential distribution

Assume a collection of independent exponential random variables $y_{1}, \ldots, y_{n}$ with means $\mu_{1}, \ldots, \mu_{n}$; where $\mu_{i} = \beta_{0}+\beta_{1}x_{i}$. How can I find the profile ...
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49 views

### Asymptotic property of tuning parameter in penalized regression

I'm currently working on asymptotic properties of penalized regression. I've read a myriad of papers by now, but there is an essential issue that I cannot get my head around. To keep things simple, ...
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44 views

### Mixed-effects model for a strongly unbalanced design

I am somehow unsure on the best option to analyze these data. Here is my study case: The response variable is a morphometric measure, one for each individual. During 10 years, say 2000-2009, people ...
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38 views

### A better bayesian way of modelling autoregressive mixtures

I have a JAGS hierarchical model which includes a temporal sub-model for the primary vote share between four party groups (LNP, Labor, Green, and Other). For each day in the temporal model, the vote ...
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36 views

### Poisson regression for change in count following an event

I have a count of sickness absences before and after an accident, and I want to find out whether an accident increases the sickness absences differently in different groups. I'm trying to formulate a ...
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53 views

### Analysis of randomized experiments

I have data from an experiment in which participants were randomly assigned to one of two groups and asked a series of opinion questions. One group, the control, was not presented with any additional ...
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34 views

### How to form a confidence band around the trend fitted from time series data

I have a time series data set. I can decompose it and get the trend but I would like to put confidence ranges around the trend (past) not the forecast-ed component. The decompose function also ...
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37 views

### Latent Semantic Analysis - Co-occurrence of words

Let $A[n\times m]$ represents the term-document matrix, where, $n$ is the number of terms and $m$ is the number of documents. This matrix can be composed into 3 matrices (SVD decomposition) such as, ...
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53 views

### Hypothesis test on the Euclidean length of an unknown vector

Question Suppose I observe a vector $\mathbf{x}=[X_1 \ldots X_n]$, where each $X_i=m_i+n_i$, with $n_i$ being an independent zero-mean Gaussian random variable with variance $\sigma^2$ (i.e. ...
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62 views

### How does LASSO select among collinear predictors?

I'm looking for an intuitive answer why a GLM LASSO model selects a specific predictor out of a group of highly correlated ones, and why it does so differently then the best subset feature selection. ...
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62 views

### How to do a multiple regression with ARIMA using R?

I am analyzing some tree physiology data (transpiration) in relation to a number of environmental variables (many of which are predictors such as temperature, PAR and vapour pressure deficit). I ...
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120 views

### Mixed models and normally distributed random effects

I am attempting to analyze some data that includes 10 repeated measurements on 10 different samples. This would normally require using mixed models, and I have attempted to model these using ...
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45 views

### How to evaluate differences of multiple likert scale ratings of multiple items within groups?

I have data where different reviewers rated how important multiple topics are on a scale of 1 to 5 (likert scale). Each of the topics is assigned to a group. I want to see if there any differences in ...
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81 views

### Kolmogorov-Smirnov and bootstrap

The KS test uses the statistic $$D_n=\sup_x |\hat{F}_n(x)-F_0(x)|$$ where $F_0(x)$ is the distribution to be tested and $\hat{F}_n(x)$ the empirical distribution. Under the null hypothesis $D_n$ is ...
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115 views

### Are GAMMs/GLM the best choice for calculating number of germs on hands?

We would like your opinion on whether GAMMs are a good option and how best to go about implementing for the following: During a period of patient care, a nurse will accrue $Y$ colonies of bacteria on ...
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63 views

### binomial test for testing significance of classification very sensitive to hits count

I'm doing a multi-class classification task and I wonder if I'm doing the binomial test correctly since it is very sensitive to the count of correctly classified trials (hits count). Say, there are ...
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88 views

### Unbiased hypothesis tests

Is there some textbook or expository account showing that the definition of "unbiased test" bears the same sort of relation to "unbiased estimator" that interval estimation generally bears to ...
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48 views

### Analyzing variables which are bound by [0,1] in R (and in general)

I'm compiling some data for econometrics research. $Y$ is the dependent variable, which is a probability index (the Simpson Biological Diversity index): D = 1- \sum \frac{n\cdot ...
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37 views

### Modeling pass rates for departments and courses within a school

Suppose I have a regression model, for example a logistic regression model, which provides a score between 0 and 1 reflecting whether or not that a student will pass a course given certain variables: ...
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58 views

### Linear mixed effects model structure feedback

We are investigating the effects of a treatment (versus untreated control) on insect abundance. The study consists of 5 geographically separated study site replicates. Treatments were applied to 1 ...
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76 views

### When to use a chi-squared test?

This is a very basic question however I do not have a statistical background and I am currently analysing some data for my dissertation. I have constructed a survey about healthy lifestyles & ...
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54 views

### Cluster on high dimensional categorical data (Images with keywords)

We're looking for clues to perform a Cluster Analysis in a DB with +400K images which have keywords associated to them. Each image could have from 1 to 30 keywords. Total keywords count is +35K. ...
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28 views

### How to randomize the tips of a functional trait dendrogram?

I have generated a functional trait dendrogram using species x trait and plots x species matrices through dbFD in package FD. I want to randomize the tips of the ...
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53 views

### Testing for mutual exclusivity

So first, sorry if I use non-standard vocabulary, since I am not an expert. Please feel free to correct. I would like to know if a set of genes in a patient cohort are mutated by a mutually exclusive ...
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199 views

### Unable to fit negative binomial regression in R (attempting to replicate published results)

Attempting to replicate the results from the recently published article, Aghion, Philippe, John Van Reenen, and Luigi Zingales. 2013. "Innovation and Institutional Ownership." American Economic ...
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42 views

### Understanding a split plot

Can someone explain the intuition behind the split plot. From what I understand, its is essentially restricted randomization. But I still quite understand it. Is there a resource or example anyone can ...
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116 views

### R-squared in linear model verses deviance in generalized linear model?

Here's my context for this question: From what I can tell, we cannot run an ordinary least squares regression in R when using weighted data and the survey package. ...
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85 views

### Using priors to detect an effect? logistic Bayesian regression

I have designed an idea and am looking for similar approaches in other literature/areas or if I have applied the Bayesian concepts wrongly. Here is a statement of my problem: I am modeling the ...
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58 views

### Distribution of variable

How to find the distribution of $$\sum_{i=1}^n (X_i - X_{1:n}),$$ where $X_i$ are i.i.d. random variables and $X_{1:n} = \min(X_1,X_2,...,X_n)$? I need to find the distribution in a particular case, ...
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65 views

### In a Monte Carlo approximation of a product of expectations, can the same samples be used for both expectations?

I am trying to approximate a product of expectations: $\mathrm{E}[f(x)]\mathrm{E}[g(x)]=\sum_x P(x) f(x) \sum_x P(x) g(x)$ with $N$ Monte Carlo samples $(x_1,x_2,...,x_N)$ from $P(x)$: ...
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100 views

### Specification of error terms in aov() in R

For a two-way repeated measures design, we can specify the model using aov in the following fashion: ...
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109 views

### Likelihood ratio test: $f(x)=2x$ vs $f(x)=3x^2$: $2n$ degrees of freedom?

Suppose $X_1, . . . , X_n$ are i.i.d. with pdf $f(·)$. We want to test the hypotheses \begin{align} H_0 &: f(x) = 2x , \;\, \text{ for } 0 \le x \le 1, \text{ against}, \\ H_1 &: f(x) = 3x^2 , ...
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71 views

### Are there terms to distinguish between the two types of outliers?

I hate talking about "outliers," because I view that term as encompassing two entirely different concepts. The first is when it refers to data that was incorrectly recorded or measured. For ...
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58 views

### Reasons for transforming multiple class classification problem into a set of binary sub-problems?

Does anyone know of a good reference that list the reasons for transforming multiple class classification problem into a set of binary sub-problems? In response to comment: One reason to transform a ...
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150 views

### Statistics for machine learning, papers to start?

I have a background in computer programming and elementary number theory, but no real statistics training, and have recently "discovered" that the amazing world of a whole range of techniques is ...
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416 views

### Validation: Data splitting into training vs. test datasets

I was naively validating my binomial logit models by testing on a test dataset. I had randomly divided the available data (~2000 rows) into training (~1500) and validation (~500) datasets. I now ...
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39 views

### Zipf's vs Self-similar: are they really the same

Recently I ran into a test using both zipf's and self-similar generated datasets. I followed the description from Jim Gray's paper on generating such datasets (Quickly Generating Billon-Record ...
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43 views

### Calculating confidence intervals for prevalence differences

I would like to calculate the confidence intervals for prevalence differences. If I have the CIs for the prevalence, can I simply subtract the upper limit of one Ci from the upper limit of the other, ...
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155 views

### Difference in chi square for factor analysis

A couple of questions relating to factor analysis I am conducting. Parallel analysis suggests 5 factors (or possibly 6) for my model and both make clinical sense. However, the seventh factor only has ...
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71 views

### PCA or no PCA. Which results are true

I am trying to correlate hundreds of geoclimatic variables with genetic data. When I do individual tests, I find several significant correlations. Then I went ahead and performed PCA on the ...
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75 views

### Estimating parameters using Kullback-Leibler and Nelder Mead

I want to find the parameters of a model which specifies a set of classification probabilities, for say M classes. (I'll use the parameters in another model later.) Given a set of parameters ...
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92 views

### What is the best test for validating trends in time-series data?

I have annual temperature data from a variety of weather stations in the Caribbean and I want to be able to show statistically that the trends for each station are significant, either positive or ...
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104 views

### Spatial autocorrelation of non-homogeneous point data in irregularly shaped sample plots

Let's assume we registered the position of all individuals of different plant species within 3 irregularly shaped sample plots that are very close the each other. As an example, I put 2 pictures with ...
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50 views

### Bounds for the population variance?

Suppose we have i.i.d. samples $x_1$, $\ldots$, $x_n$ for a (potentially non-normal) random variable $X$ with finite moments. We can use these samples to construct an unbiased estimates of the ...

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