# All Questions

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### Confidence intervals of error on non-normal distibution

I am trying to test the hypothesis that value $x$ is a predictor of value $y$. However, $x$ is a value that is computationally intensive to calculate in many cases. In some cases, I can generate $x$ ...
2 views

### What happens when I “flag” (set to 0) small loadings to compute factor / component scores?

In Q Methodology, it is common to logically flag (where FALSE sets the loading to 0) small or "insignificant" factor/component loadings before computing factor/component scores – prior to calculating ...
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### How can I create a logitnormal variable in pymc

I would like to use a latent variable which is LogitNormal Distributed in pymc. Can I do this in pymc ? https://en.wikipedia.org/wiki/Logit-normal_distribution. I dont see a standard class like I ...
7 views

### Uncertainty in angular velocity (ω)

What is the uncertainty in angular velocity? Formula for angular velocity ω is: $2 \cdot \pi \cdot f (\text{frequency})$ $f = \frac{1}{T\, (\text{period})}$ so the formula for $ω$ can be ...
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### Which Algorithms for predictive recommendation?

I have a training data set with 10m user ratings of movies, (expanded MovieLens) and 25 features (movie information, release, genre etc). I want to design and build a recommendation system that will ...
7 views

### Alternative to a coefficient of variation

I am currently collecting data 4x per week with a fencing athlete. She jumps with each foot on a separate force plate, so we can see asymmetries in force curves. We noticed that whenever she is more ...
6 views

### Differences between normal SVM and SVM Linear? [on hold]

What actually differences between normal SVM and SVM Linear? I already trained my data using RapidMiner with both models but it shows same results in terms of accuracy. Please advice. Thank you.
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### Classifying the F7 (First 7 days Activity)

In social networks we have a commonly used metric called F7. It is the number of days a user logged in during their fist week since sign up. This means it has a range of [1,7] since you must at least ...
17 views

### Apparent Contradiction in Inverting Linear Regression

I believe this is a basic question, but I still can't seem to figure it out. In linear regression, if the standard deviation of the x-data and the y-data is 1, the slope of the best fit line is the ...
11 views

### Interpreting multiple linear regression with continious moderating variables

First some background information: I am doing a study that examines whether number of patents and trademarks (2 independent variables) influence gross margin (dependent variable). Now I speculate that ...
6 views

### Comparing AIC/BIC Between Continuous (CFA) and Categorical (LCA) Latent Models

Some colleagues and I have a set of variables that we would like to represent more parsimoniously/latently. Originally, my colleagues used an exploratory and confirmatory factor-analysis approach to ...
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### RESET Test in R Influenced by Heteroskedasticity in the Data?

I'm running a negative binomial model in R on 558 observations of count data, along with "vcov" to add robust errors. I am using the Ramsey RESET Test as a criteria to judge my model. I have always ...
13 views

### Probability Questions within R

I'm learning about Probability with Binomial, Poisson and Normal Distributions. I came across some study examples on-line that ask you to do it within R. I was given 10 exercises which were: I did ...
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### mixed effects and lme4: Do I need nesting?

I am analyzing data from a field experiment, and I am interested in the effects of fauna and altitude (fixed). Altitude has two levels, and at each site I have 5 blocks for the three levels of fauna ...
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### interpreting multinomial logit model results in R [duplicate]

How can i interpret the results from a multinomial logit model in R where I have used categorical variable as an individual specific variable such as gender. Are the results in terms of frequency? ...
18 views

### Why standard deviation of population is unknown in t test

Why mean of the population is known but standard deviation is unknown ? Mean is calculated from individual values then why can't standard deviation be calculated? Is there any practical scenario where ...
15 views

### One sample hypothesis test of a proportion [on hold]

In a random sample of 25 people 45% say they believe in ghosts. Rounded to two decimal points, the test statistic for the null hypothesis that the true proportion of people in the population who ...
17 views

### If a newspaper article reporting on a study states that the researchers found a result of the study to be significant [on hold]

a. the result may be significant in the statistical sense, but not in the everyday sense of the word. b. the P value for the must have been very large. c. the effect size must have been large. ...
14 views

### Longitudinal Cluster Analysis

I have data with subjects, 4 observations each, ordered by time (4 time points each). And, I have some additional numerical variables. I want to perform a cluster analysis to see if there are any ...
10 views

### Bayesian association testing and simulation

I read some Bayesian references recently and came up with some basic or naive questions about Bayesian inference. My research question is to test the association between predictors and outcome, and it ...
11 views

### Why is Fama-Macbeth Estimator simply Mean group estimator?

I was reading this blog post about using R to perform Fama macbeth regresion: https://landroni.wordpress.com/2012/06/02/fama-macbeth-and-cluster-robust-by-firm-and-time-standard-errors-in-r/ I am ...
15 views

### Difference between ρ and ρ hat

I was reading a paper where the author mentioned using ρ (correlation coefficient) and then the formal showing how to calculate correlation coefficient contained ρ hat. So I am wondering if these are ...
5 views

### How to implement a two-level beta regression?

I am working with Time-series Cross-section data and my response variable is a proportion ranging from 0 to 1 (including 0 values but no 1s observed). Beta regressions, and especially the fracreg ...
11 views

### How to deal with a model that can't be fit due to quasi-complete separation? [duplicate]

I am doing a binary logistic regression analysis. I got one categorical predictor with 7 levels. When I try to do this in Minitab 17 I get an error message: "The model could not be fit. Maximum ...
6 views

### Excluding levels in a categorical predictor in logistic regression

I am doing a binary logistic regression with one explanatory variable. I got 7 treatments originally in this variable, but what I am actually interested in is testing the difference between two of ...
11 views

### how can I check the bias between two groups

I have a presentation at the firm... using the stata. I want to check is there any bias between unweighted mean and weighted mean. and I already calculated the means between them..by common method ...
17 views

### How to calculate Cronbach's alpha

For my dissertation I am observing horse race videos to see if horses are right or left handed. In flat races where the horse comes out of the starting stalls I observe which leg (right or left) they ...
19 views

### Don't understand the symbol of the formula [on hold]

I have a formula of this picture below from the application Minitab. The problem is that I din't understand the strange symbol (inside of the red mark selection) in order to make a calculation. Do ...
6 views

### opennlp no parse for statement [on hold]

while performing entity co-referencing using opennlp – for some of the statements I get an error “Couldn’t find parse for “. What could be reason? whole execution stops. But if I set reportFailedParse ...
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### Chi squared test for differences between constructed variable

Let's assume I have a control and a treatment group with 1000 participants each and I ask each of them three questions regarding their risk perception. Each of the three questions is concerned with ...
6 views

### R SVM text classification error [on hold]

R text classification sometimes gives below error - what could be reason? Error in validObject(.Object) : invalid class "matrix.csr" object: ra has too few, or too many elements Calls: ...
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### statistics to use for a mobile based health intervention aimed to increase physical activity

I am trying to understand how a mobile application will increase the number of steps taken. We are measuring their BMI and waist circumference before and after 6 months and taking measurements of the ...
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### Probability of failure

A structure will fail if subjected to a load greater then its own resistance: failure := load > resistance We can assume that the load and the resistance are ...
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### Relationship between the growth rates of quarterly and yearly series

From a quarterly series, I get the corresponding yearly series by summing up the four quarters of each year. The quarterly growth rates are calculated over the same quarter over previous year (and not ...
16 views

### machine learning to predict unknown future positions of a vehicle

I want to predict the future steps(arbitrary physical location) of a vehicles trajectory using machine learning algorithms at least 4 to 6 seconds ahead. Currently I have tried to predict before 6 ...
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### Excluding cases before or after calculating mean-centered variables?

I stumbled upon the following problem and was wondering how to address is adequately: I have a large dataset with around 60 groups, each of them with 4-6 people. For my study, each participant's ...
18 views

### Relationship between event and random variable?

I've been told that an event is just a random variable that has been assigned, and that random variables are a generalisation of events. However, I can't relate that to the definition of an event as a ...
18 views

### How to make a 2-way ANOVA graph cleaner? Is there another test for these data?

I'm working with data from an experiment where we tested 4 different concentrations of a drug on cells, plus the same drug but inhibited, an inert protein (BSA) and the medium only control. We also ...
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### Bayes theorem in odds form - incorrect in Tetlock's 'Superforecasting' book?

Page 170 in Philip Tetlock's et al. Superforecasting book shows Bayes' theorem in odds form as: $$\frac{P (H|D)}{P (\neg H|D)} = P (D|H) P (D|\neg H) \frac{ P (H)}{P (\neg H)}$$ Posterior Odds = ...
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### Sampling vector so they will have a given euclidean distances matrix

Given a matrix $M\in\mathbb{R}^{P\times P}$ , is it possible to sample $P$ vectors $u_i\in\mathbb{R}^N$, $i=1..P$ so that $\|u_i-u_j\|=M_{ij}$. Obviously for not any $M$ this is possible, i.e. it has ...
16 views

### Aggregating standard deviation to a summary point

I have a range of data (server performance statistics) is formatted as follows, for each server: ...
4 views

### Odds of specific generated population of exponential distributed stochast

I'm trying to generate a sequence of samples using an exponentially distributed stochast, i.e., making a Poisson arrival process. In my specific case I generate 337 samples using a lambda (rate ...
13 views

### Fit error-in-variables polynomial regression using mle2 (R)

I need to fit a polynomial regression that accounts for measurement errors. I found out how to do it with a mcmc model (using RJags) and I would like to do it with a Maximum Likelihood Estimator ...
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### Cluster into communities a graph with negative edge weights representing repulsion

Consider an undirected graph $g$ with some edges having negative weight - all weights in $[-1,1]$. We are seeking communities or clusters. Negative edge weight means repulsion and positive means ...
5 views

### Comparing 2 treatment groups in a randomized experiment

Good morning, I am drafting a randomized experiment testing the effects of A. an increase in quantity of kcal assumed in meals B. an increase in the quality of meals (quality defined both in terms ...
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### Where can I find the documentation of syntax for Alogit (the Conjoint analysis software)? [on hold]

I have to use the Alogit conjoint analysis software (http://www.alogit.com/) in a conjoint study but I can't find any complete documentation on all the modelling syntax available to use in its ...
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### Recurrent neural network for object tracking & position filtering?

Would a recurrent neural network be appropriate for object tracking tasks? Mainly I will have 3D feature vectors $(x, y, t)$ where $x$ and $y$ are the positions of an object in the image and $t$ is ...
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### Can I use k-folding to train a model without testing set?

If I have few data, testing the model can be a problem as I have less data to train it, so I would like to know if it is possible to generate a model with all data I have, and give as AUC the mean of ...
It seems that whenever neural networks can be applied successfully, there are sufficiently many local minima on the optimization surface $S(\mathbf{w})$ (as a function of the weights $\mathbf{w}$) ...