# All Questions

28 views

### PCA and degrees of freedom

I had thought that a principal components analysis gives us information about the number of degrees of freedom (i.e. independent variables) underlying a system which we may only be able to observe ...
7 views

### Anova: 'Base case' for interactions when regressing upon dummies

Say I want to perform a two-way ANOVA, and I want to use the sources A, B . For A I test at levels A1 and A2, for B at B1,B2 and B3. So when I do the analysis I regress on the dummies with, for ...
21 views

### Fitting multilevel models to complex survey data in R

I'm looking for advice on how to analyze complex survey data with multilevel models in R. I've used the survey package to weight for unequal probabilities of ...
18 views

### Statistical testing: Multiple classifiers, 1 domain. Would rANOVA be appropriate?

When comparing the performance of two classifiers over a single domain, in the context of a classification problem in machine learning, it is common to use a paired t-test, using the 10 average ...
53 views

### Superiority of LASSO over forward selection/backward elimination in terms of the cross validation prediction error of the model

I obtained three reduced models from a original full model using forward selection backward elimination L1 penalization technique (LASSO) For the models obtained using forward selection/backward ...
19 views

### I'm stuck: How to 'bin' multiple binary outcome variables and then analyze within subject?

I have what feels like it should be a very easy analysis to work out, but I've been trying for hours and I can't figure it out. I'm using SPSS by the way. I have 10 (5 of each group) different binary ...
17 views

### Parameter Estimation of a Poisson mixture model

I want to estimate the parameters for a Poisson mixture model with 2 (and later 3) Poisson distributions. I want to use Matlab and have numerical problems to solve the loglikelihood of the mixture ...
30 views

### Optimizing False Negative Rate after Logistic Regression

I created a probit model and tested it against a random sub sample of my dataset. I am interested specifically in seeing how many data points I can predict to be FALSE without having too many that are ...
43 views

### Probability density function within [0,1] with specifiable mode

I needed a probability density function which worked on the interval $[0,1]$, had kind of a bell shape, and had an adjustable mode / peak $p$. I thought of a pdf $f(x|p)$, given by ...
27 views

### R as a backend processing engine [on hold]

I have an R script that process a CSV file and spit out result as CSV. This work fine in desktop environment. Now I would like to implement some think like this: set up an email where user could ...
32 views

### predict function and categorical variables in R

This is more of a general question about how the predict function treats categorical variables and how to interpret the output from predict. I have a zeroinfl model to predict the number of animals ...
17 views

### How to cluster users based on search terms

How to cluster based on what users are searching on I'm working on an app which includes search functionality: a search box that allows a user to enter text and search the entire site. I have access ...
170 views

### Real life examples of distributions with negative skewness

Much along the lines of the "real-life examples of common distributions" I'm interested if anyone has any pedagogical examples used to teach negative skewness? There are plenty of canonical examples ...
9 views

### Simulating EM versus listwise deletion--unexpected results

I'm preparing a presentation on missing data strategies and conducted a simulation to compare listwise deletion (LD) to the EM. Here's what I expected based on the literature: Standard errors will ...
49 views

33 views

### CSV file to numeric [on hold]

I I read a csv file. Now I need to convert it to numeric, but how? data = read.csv("c:/osz.csv", sep=";", header=FALSE, dec=".") ...
27 views

### How to account for autocorrelation in a multiple linear regression?

I'm trying to create a multiple linear regression with water temperature change as my response variable and four numeric explanatory variables (that influence temperature change). Each numeric ...
12 views

### Comparing two distributions using Generalized method of moment estimation

If I consider a data X, I want to fit a distribution Y which has a density f(x) but It's not possible to express the moments of Y as function of the parameters. My problem is : 1- to estimate the ...
8 views

### Issue With class imbalances in classification problem

I am working on a word sense disambiguation problem. Specifically, I am using decision lists to classify the ambiguous word. Decision lists work in the following way. The quantity ...
10 views

### Standardizing inputs for CART

I know I do not need to standardize the predictor variables before applying CART but would there be any adverse effects to doing it anyway? I'm comparing CART to a linear regression where I did ...
33 views

### ldentifying observations on the edges in heteroscedastic data

Consider bivariate data consisting of correlated variables (r ~ 0.9). It is known how both the variables are calculated. Each observation is identically distributed but non independent. Also, the ...
74 views

### Time series prediction: visualising path uncertainty region

I am predicting a time series' future evolution and am evaluating the path uncertainty using bootstrapping. Is there a good way to visualise the uncertainty that goes beyond simply plotting a pair of ...
147 views

### General method for deriving the standard error

I can't seem to find a general method for deriving standard errors anywhere. I've looked on google, this website and even in text books but all I can find is the formula for standard errors for the ...
24 views

### Probability of object collision

I've been searching for a few days on a number of sites but I can't seem to find a good answer for this. I'm developing a collision detection program using Unscented Kalman Filter and predicting ...
15 views

### Experiments for performance testing software

I am looking to run a series of performance tests for a software system across different configurations and determine which combination works best. The software system processes a number of files, ...
8 views

### How to perform ANOVA on a modification of the dataset?

I just started working with R and I could really use some help with this problem. I want to perform an ANOVA, to see how my independent factors (between-subject: Group) (within-subject (Modality, ...
18 views

### Multiple covariates in an ANCOVA design

I have found a group difference (3 groups) for my dependent variable and now I am supposed to find out if possible covariates influence this finding. What is the best way to "correct" for 5 ...
16 views

### Growth curve analysis on orthogonal polynomial terms

I am conducting a study which is looking at the effect of 'Condition' (Quiet, Intelligible, Unintelligible) on the pupil(eye) response over time. Upon visual inspection of my data plots, pupil ...
15 views

### Probabilistic modelling MCMC question with pyMC

This is my first post and I am a newby in pymc. I am trying to model a non-linear system (see below for a further explanation). I create my synthetic data with: ...
34 views

### String clustering and centroid computation

I have a text file document containing a set of words strings that I want to cluster. I want to use the K-means algorithm. As a ...
16 views

### Fixed, random effect and nested factor in lme

I have a dataset with the following variables: Treatment : (fixed,3 levels) Location : (fixed, 4 levels) Sample (random, 5 levels): 5 samples are taken in each location (randomly) Subsample ...
14 views

### Moving certain elements of data frame into new columns (in R) [migrated]

I have a data frame in R looking like this: jiz<-data.frame(Type=c("X","B","B","B","B","X","B"),Action=c("both","1","2","2","1","both","1")) Type is either X ...
17 views

### Trend Analysis to determine threshold [on hold]

I have a social media trend data for various months. For each channel I need to determine wheather to continue investing in a channel based on the audience engagement. So basically I need to set ...
26 views

### Keywords to find academic lectures on multivariate time series analysis on youtube

If I search for "HOTT homotopy type theory" on youtube, I find numerous (advanced/state-of-the art) academic lectures on the topic. For instance the following lectures are found on youtube: ...
17 views

### comparing means between different studies

In a questionnaire, I have asked some Likert scale questions. These questions were asked to the same population 6 years ago in another study. I only have the mean scores and standard deviation of the ...
42 views

### What are the important conditions in ANOVA fixed effects?

I am working with an ANOVA model. I want to run a fixed effects ANOVA in which I have a ratio dependent variable and three independent variables with two and three levels. Obviously, before analyzing ...
25 views

### coefficients extracted by effects package in R

Consider this logistic regression: mtcars$vs <- as.factor(mtcars$vs) log_reg_mtcars <- glm(am ~ vs*wt +vs*mpg, family = "binomial", mtcars) I tried using ...
4 views

### ARDL, Lag Terms and Singularity

I am interested in fitting an ARDL model that has 4 lags for each explanatory variable. However, when I fitting the model in R. R says that coefficients are not defined because of singularities. Is ...
19 views

### How to make WinBUGS close when “Trap” occurs [on hold]

I'm using R2WinBUGS to process several datasets in WinBUGS in "batch mode". Occasionally traps occur, mainly due to bad parameters (I guess), and I managed to avoid ...
46 views

### Probability of webpage accessed in a particular hour

I want to programatically calculate at which particular hours of a day the probability of a webpage hits(accessed) are high. Which statistic formula should I use to calculate the peak hours of the ...
58 views

### Prove the equivalence of the following two formulas for Spearman correlation

From wikipedia, Spearman's rank correlation is calculated by converting variables $X_i$ and $Y_i$ into ranked variables $x_i$ and $y_i$, and then calculating Pearson's correlation between the ranked ...
7 views

### Difference between point-biserial and rank-biserial correlations

According to the wikipedia article the point-biserial correlation is just Pearson correlation where one variable is continuous but the other is dichotomous (e.g. Yes/No, Male/Female). However the ...
30 views

### Logistic Regression using dummy variables in MATLAB

I have a model where categorical (mutually exclusive) variables predict bankruptcy. Chi-square is significant. How can I code a logistic regression model in MATLAB ...
23 views

### Estimating a confidence interval around the average of an interacted treatment effect

I've got a causal inference situation with heterogeneous treatment effects. In addition to simply estimating coefficients, I'd like to get an average effect of the treatment at the covariate values ...