# All Questions

21 views

### Is $R^2$ valid in a nonlinear model?

The question is in the title. The coefficient of determination or $R^2 \equiv 1 - \frac{ss_{res}}{ss_{tot}}$ is valid in a nonlinear model? Why?
9 views

### How to validate % answering Yes/change exists is enough to say population is seeing a new pricing model?

I have a survey on pricing. There are questions where there is an A and B choice where the proportions are not independent (mutually exclusive group). Here I can use a binomial distribution in Excel ...
7 views

### Friedman test block contents

For comparing computational intelligence algorithms over multiple functions I have seen the Friedman test used like the following [1]: ...
7 views

### R modeest package: Which method of mode estimation?

I have a unimodal continuous distribution which is skewed and I would like to estimate the mode using the modeest package in R. However, the package offers a relatively large number of methods to do ...
13 views

### Summing variance of autocorrelated timeseries

Problem: When trying to calculate the variance of timeseries sums I get a negative variance, mostly due to autocovariances at large lag steps. Does not seem realistic. I have a timeseries which is ...
7 views

### similarity measures with missing values

How to handle missing values when computing similarity (or distances)? (I have binary feature values and do use the simple matching coefficient, but I feel that the answer to this question may be more ...
8 views

### Software package to generate a pdf of a normal distribution of data stored in a Matrix?

Is there any software package to generate a pdf of a normal distribution, where that package can take data points stored in a Matrix as a whole and return pdf of the individuals of the Matrix? ...
14 views

### Cramer-von Mises using pdf instead of Cdf

Cramer-von Mises gives a nice way to compare distributions with: $$\int [(\hat{F}_n(x) - F_0(x)]^2dF_0(x);$$ I'd like to use something like this to compare two empirical distributions, is there ...
22 views

### How to analyse my time serie experiment

I have a question about how I can analyze the data from a time series experiment. I'm still a student and therefore am not really familiar with all the procedures and analyzes in SPSS, so i hope ...
17 views

### Should the mean of the bootstrapped distribution always be asymptotically equal to the sample estimate?

Suppose I bootstrap the distribution of the sample mean. Normally, one would use the mean of the bootstrapped distribution as point estimate of the parameter and the s.d. as its standard error. The ...
6 views

### CAR spatial models in JAGS

WinBUGS comes with the GeoBUGS add-on, which contains a number of predefined model structures that are suitable for modelling spatial data structures e.g. geostatical structures (spatial.exp), ...
8 views

### Validating a model with 2 random effects and fixed effects of different levels

I have been working on this problem for the last little while and trying to write out the code to the below math/description for an ecological dataset in lmer, but I wanted to check with a few people ...
10 views

### Interpreting the results of a GLM with two non-ordinal and “correlated (not sure of the term)” explanatory variables

Consider this data that are created by the following ugly code: ...
19 views

### Confusion related to the dual being concave

I have some confusion related to the dual function or the Lagrangian being concave for a general convex optimization problem with objective function $f_0(x)$ and equality and non equality constraints ...
9 views

### Unstandardized effect size for two non-equal size samples for experimental design in R

I am trying to calculate the required (unstandardized) difference in between a test and control group of different sizes. I have historical data with transactions for the test group (n=272, mean ...
9 views

### 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 ...
23 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?
17 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 ...
14 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 ...
21 views

### 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 ...
17 views

### 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 ...
11 views

### 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 ...
9 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 ...
20 views

### Calculating Autocorrelation in R with acf [migrated]

I am trying to calculate the ACF by usingcor function in R. Also trying to replicate the results from this site: ...
26 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 ...
23 views

### How to convert 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? Thank you.
13 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 ...
8 views

### 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 ...
60 views

### How can I generate uniformly distributed points on a circle?

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 ...
56 views

### Is my Poisson regression correct?

Here are my data: ...
44 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 ...
33 views

### 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 ...
28 views

### 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 ...
10 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 ...
15 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 ...
10 views

### 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 ...
19 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 $W = p_1*p_1'$ ...
10 views

### 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 ...
25 views

### 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 ...
33 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 ...
11 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 ...
18 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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16 views

### 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 ...