# All Questions

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### Inter-coder reliability for continuous data and 4 coders

I've had four students coding the frequency of certain verbal and nonverbal behaviours. In hoping to generate some sort of intercoder reliability, I've had them all code the same 10 interviews. For ...
4 views

### Gaussian RBF vs. Gaussian kernel

What is the difference between doing linear regression with a Gaussian RBF basis and doing linear regression with a Gaussian kernel?
4 views

### standardize two categorical variables into same unit

I have two categorical variables that I want to add: fruit portions = portions of fruit per day (a portion representing a handful): 1= never to 7=5 or more portions, and fruit juice frequency = how ...
7 views

### Is a p-value correction necessary for assessing pairwise location shifts on centered data?

I am currently assessing whether or not a location-shift can be assumed in non-parametric comparisons to be able to formulate the rejection of the null hypothesis in other terms than the probabilistic ...
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### Minimizing Relative Error (or mean square error) and Maximizing Likelihood

I'm not a statistician, so I would appreciate an answer in the simplest possible words. I've read that, in some sense, when we minimize the mean square error, we are maximizing the likelihood. This ...
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### Stationarity in multivariate time series

I am working with a multivariate time series and using VAR (Vector Autoregression) model for forecasting. My doubt is What does stationarity actually means in a multivariate framework. 1) I know ...
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### Estimation of residual variance in regression

I'm doing different regression tasks based on models of the form $y=m(x)+\epsilon$ where $y$ is vector valued data, $m(x)$ is the output of a computer model and $\epsilon \sim N(0,V)$ is a multinormal ...
8 views

### How to combine complete regression coefficients?

How I can combine hazards regression coefficient in meta analysis? I want to have a complete regression from combing hazard regression with different covariates. I mean some of them have additional ...
18 views

### Calculating Autocorrelation in R with acf

I am trying to calculate the ACF by usingcor function in R. Also trying to replicate the results from this site: ...
21 views

### Fitting a “pseudo” discrete dataset

I'm working with a dataset that contains information about consumption of apples. The dataset contains the amount of apple consumed in g/day. The problem with this is that the data points fall into 3 ...
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### How to understand LS means into arithmetic means?

SAS PROC GLIMMIX output contains series of statistics for LS Means: . How to convert them into arithmetic mean related ones? Where do I have to read about these column notations in a non deep ...
11 views

### How to build a relevant text classifier?

I would like to build a message classification system which classifies a given message into either of 2 class - Relevant/Not. I don't have any labelled dataset. I only have certain keywords which ...
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### Testing time homogeneous Markov chains

I am working with different transition diagrams and want to calculate the likelihood ratio statistic for testing time-homogeneous. I saw that there are already some comparable questions, but I still ...
41 views

### How can I generate uniformly distributed points on the surface of a hypersphere?

I am looking to generate 450 data points in R. There are three distinct sets 150 of each distributed in a circular band with different radii (at 1, 2.8 and 5). In particular, I'm looking to reproduce ...
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### Is my Poisson regression correct?

Here are my data: ...
38 views

### How exactly is sparse PCA better than PCA?

I learnt about PCA a few lectures ago in class and by digging more about this fascinating concept, I got to know about sparse PCA. I wanted to ask, if I'm not wrong this is what sparse PCA is: In ...
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### Statistical Problem

A psychiatrist hires you to study whether her clients self-disclosed more while sitting in an easy chair or lying down on a couch. All clients had previously agreed to allow the sessions to be ...
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### Statistical problem / explanation [on hold]

A researcher studied the effect of television violence on concentration of a particular blood chemical. In this study, 40 participants were measured over a period of an hour prior to watching a ...
8 views

### Calculating Second-Order Tikhonov Regularization Parameter in Mathematica

I am trying to map slowness of underwater sound velocity in a river using some tomographic device. The location of each acoustic receiver/transmitter is shown in the picture below To find the ...
14 views

### Predicting data based on two data sets

I'm brand new to SAS programming, and I'm having difficulty figuring out this issue: I have two sets of data 1st set has 4 columns (income is a continous range of numbers, sex is 0 for male - 1 for ...
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### Time Series Forecasts of Appointments with Pre-Reqistration

Looking for some tips and ideas. I get a list every day of the number of appointments for each day for the next two weeks for a clinic. I have quite good history of these list, and the actual number ...
16 views

### Comparing linear regression models created from different data sets

I have one linear regression model [Mold] created from 12 points where I can calculate a single value of RMSE between the predicted values and the actual observed values. This model is then used to ...
16 views

### On the application of an algorithm for classification

Given, a set of training pattern p_1 = [1 -1 -1 -1 -1 1 -1 1 1 1 1 -1 -1 1 1 1 1 -1 -1 1 1 1 1 -1 1 -1 -1 -1 -1 1]'; I can calculate the weight by $W = p_1*p_1'$ ...
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### How many different random initializations should I perform with Lloyd's algorithm to obtain the optimal clustering with X% of confidence?

I use Lloyd's algorithm for clustering. Since it relies on a random initialization and Lloyd's algorithm can get stuck in local optima of the k-means objective function, I have to run it several ...
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### How to determine if % selecting Option A is statistically different from selecting Option B in a survey?

I ran a survey on pricing and asked respondents to choose between option A or Option B. 61% chose option A and 39% chose Option B. The sample size is 90. How do I determine if the % selection Option A ...
9 views

### How much do self organising maps suffer from local minima problems?

How much do self organising maps suffer from local minima problems? I assume that the original orientation of the grid can have major orientation on the resulting shape of the grid, but does this have ...
28 views

### Term is significant linearly, quadratically and in interaction?

I used deletion tests to identify ecological factors that relate to the number of parasites on rodents. There is one factor that is significant linearly, quadratically and in interaction. However, the ...
10 views

### Finding subsets with Branch-and-bound techniques

Hello I am trying to find a Matlab version of a function which performs best subset selection for least squares regression using leaps and bounds (branch and bound) approach. Like in the paper by ...
16 views

### Using caret train function to perform lm with 10 repeated 10-fold cross validation

I'm using the caret package at the moment to perform different forms of analysis on my dataset. I did the following to do 10-fold cross validation, 10 times:- ...
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### Comparison of Kaplan-Meier curves across ordered groups

I am familiar with the log-rank test for comparing multiple Kaplan-Meier curves, but I am looking for a test that will compare across ordered groups (an ordinal variable). A significant result from ...
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### What is the actual equation of the standard 68/95/99 bell curve graph? [duplicate]

I want to connect Calc with Stats via cumulative density and taking the area under the curve. However, what is the equation of the curve that models the standard 68/95/99 bell curve?
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### Coefficients from a penalized Cox PH

I'm using the R package Penalized (0.9-42) on a Cox PH model. I'm using L2 (Ridge) on the grounds that I don't want to shrink my coefficients to 0. I don't understand why when I ask for: ...
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### computing confidence interval for ranges, confidence level 0.95

I have some ranges of values and frequencies of each range. Participants choosed an entire range when asked, and not a particular value. Example: Range [0,20] : frequency = 20 Range (20,60], ...
66 views

### Best modelling packages in R?

In R I use a lot the packages plyr, stringr, Hmisc and ggplot2. Each of these packages take the base code and make functions that are more intuitive and easier to work with. Each of these packages ...
11 views

### Absolute vs. Relative Difference in Survival Time - Is this possible?

So there's a fairly well characterized difference between relative risk and absolute risk for conventional cohort studies, and for many questions, the absolute risk is arguably more appropriate. Is ...
16 views

### Why is the scatter diagram always symmetric around the SD line?

This may seem like a dumb/vague question. When you draw a line of slope $\frac{\sigma_y}{\sigma_x}$, why is this line the major axis of the scatter-diagram ellipse? Is this some property of the ...
28 views

### Calculating confidence intervall for quantiles first by hand (than in R)

It would be great if someone can check whether my approach is correct or not. Question in short will be, if the error calculation is the correct way. lets assume i have the following data. ...
28 views

### Meta-analysis with a binary response variable

I am attempting to fit a model to my data for meta-analysis I'm working on. The response is binary (0 or 1), and I want to specify a binomial distribution with logit link function. The 2-3 (depending ...
29 views

### Poorness of Kernel methods on visual pattern recegnition?

I am currently reading the recent papers mainly written by Y. Bengio [1],[2],[3]. There are very strong claims about poorness of Kernel methods on recognizing handwritings in many general cases but ...
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### Repeated measures mixed multinomial model in R - extract coefficients

I would like to perform repeated measures mixed multinomial model using R. To be exact I would like to do MaxDiff analysis similar to SawTooth Hierarchical Bayes method. I want to use mixed models ...
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### Estimating distribution from censored data

$X$ is a positive variable with known support (assume discrete support, if that simplifies solution). $Y$ is another variable with the same support. $X$ and $Y$ are independent. $Z$ is equal to $X$ ...
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### I have a problem in bayesian networks get p(E|A)

I'm doing this book "Modeling and reasoning with Bayesian Networks" and I have this problem: ...
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### Guess several distribution's parameters from a list of interarrivals

Just a small introduction to the setting: I have traffic that is generated using several layers. Layer 3 consists of the basic packets, while Layer 2 is a more high level grouping of packets, and ...
21 views

### Expectation of correlated variables

I'm looking to compare effects $\delta = \frac{\mu_T - \mu_C}{\sigma}$ for two studies, compared with the same control group. In order to find the covariance of effects for treatment A and treatment ...
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### Conditional Logistic Regression, Rare Events and R

I have a panel data set organized around 35 provincial units, with 110 binary "positive" outcomes in the dependent variable. This is for about 2600 observations in that data set. I have a couple ...