All Questions

Filter by
Sorted by
Tagged with
11
votes
1answer
2k views

How to fix a coefficient in an ordinal logistic regression without proportional odds assumption in R?

I want to do an ordinal logistic regression in R without the proportionality odds assumption. I know this can be done directly using vglm() function in ...
2
votes
1answer
1k views

How do I compare the quasi likelihood of two multi-level generalized estimating equation models?

With the log-likelihood chi-square statistics I can compare two linear mixed models (Maximum Likelihood) and see which one is the better one. But the GEE gives Quasi Likelihood under Independence ...
2
votes
0answers
273 views

Support vector machines and Granger causality

I was wondering if Granger causality would be an efficient tool for searching for relevant input data for an SVM system. For example if I want to forecast SP 500 returns, I could put in my input data ...
5
votes
2answers
92 views

Supervised classifier for events with missing data

I'm working on an experiment in which we try to sort events into three categories based on roughly 20 inputs using a feed-forward neural network (trained via backpropagation). Unfortunately, many ...
1
vote
0answers
124 views

Can we simply compare the predicted percentages of the outcome between studies?

I used the multinomial logistic regression to predict the percentages of students who voted 'acceptable', 'uncertain', and 'unacceptable' to natural ventilation use in three observed classrooms during ...
5
votes
0answers
206 views

Transferring to new domain

Suppose I have a set of characters with both natural scene and synthetic images, and another set with only synthetic images. I'd like to make a classifier which is trained on only on this data and ...
0
votes
1answer
743 views

Non-significant MANOVA with significant planned contrasts [duplicate]

Possible Duplicate: Not-significant F but a significant coefficient in multiple linear regression How can you have a non-significant multiple regression model w/ significant predictors? My ...
1
vote
0answers
152 views

What is/are good economic indicator(s) to use for predicting whether or not someone will leave a company?

BACKGROUND FIRST: I'm in the process of putting together one data file that includes various employee demograhic information for continuing employees and employees that have left the company in the ...
3
votes
0answers
2k views

Free database of historical events in database format? [closed]

Is there a free database of historical events that's in database format (ie, CSV or some other easily imported format)? I realize Wikipedia has extensive historical information, but it's not in ...
1
vote
1answer
451 views

Possible reason for failing to build a support vector machine

I was trying to build a classifier for a set of documents using a support vector machine. I choose to build the feature space using term occurrence. While experimenting, I found the following scenario:...
3
votes
1answer
687 views

Peak detection in a ucontroller using FFT

A project I am working on currently is to create a heart beat sensor using a finger plethysmograph. It returns a signal to my ucontoller that only includes positive peaks. For example, the ideal ...
10
votes
4answers
403 views

Sparsity-inducing regularization for stochastic matrices

It is well-known (e.g. in the field of compressive sensing) that the $L_1$ norm is "sparsity-inducing," in the sense that if we minimize the functional (for fixed matrix $A$ and vector $\vec{b}$) $$f_{...
17
votes
2answers
8k views

Random effect equal to 0 in generalized linear mixed model [duplicate]

Sorry if I'm missing something very obvious here but I am new to mixed effect modelling. I am trying to model a binomial presence/absence response as a function of percentages of habitat within the ...
3
votes
2answers
2k views

Dimensionality reduction on a huge binary matrix

I have a 0/1 sparse matrix with 500 k columns and 3 M rows and I want to do reduce the number of columns. Clearly I cannot load this into R, as is, so ...
3
votes
1answer
106 views

Validity of using the mean duration across a sample period as the trial for Student's t test or Welch's test

Business Problem We are measuring the duration of an operation on our server. We want to know if certain changes (call them treatments) make this operation faster or slower. Data Our current test ...
2
votes
0answers
119 views

Is there a name for distributions induced by norms?

The log density of a multivariate Gaussian is proportional to $||x-\mu||_2^2$, i.e. the norm of the difference between $x$, the random variable, and $\mu$, the mean of the distribution (assuming a ...
1
vote
2answers
181 views

Significance of different mean values for two processes

I have an experiment that produces one measurement every time it is run. I can change something in the experimental setup, and I want to test if this change in the setup results in a change of the ...
19
votes
3answers
12k views

Proof that moment generating functions uniquely determine probability distributions

Wackerly et al's text states this theorem "Let $m_x(t)$ and $m_y(t)$ denote the moment-generating functions of random variables X and Y, respectively. If both moment-generating functions exist and $...
4
votes
1answer
339 views

Predictive Probabilities

Other than a calibration plot, is there a way to decide how good one models' predictive probabilities as compared to another model. I'm not interested in error rates as I find them ineffective for ...
6
votes
1answer
6k views

How to decide which decision tree classifier to use?

I am confused about which decision tree algorithm in weka to use for my application. I have 5 real input variables and 2 classes. In various online tutorials J48 (C 4.5) seems to be the algorithm of ...
2
votes
1answer
5k views

Proper use of weights argument in linear mixed model [lme()]?

After attempting to produce a linear mixed model I was left with a great deal of heterogeneity. ...
4
votes
2answers
231 views

Advice on regression modelling

I have a large set of data for 37 different clinical units (all oncology) in their respective 37 hospitals. There are two specific outcome variables that I need to analyse: First, drug usage for ...
3
votes
0answers
945 views

How to interpret p-values for factors [duplicate]

I have fitted a Poisson model to my data in R which includes two factors as independent variables. Each factor has 5 levels. I have used the ...
1
vote
2answers
3k views

Statistical test to compare multiple treatments on the same 'individual' over time

I'm looking for a statistical test or tests to compare the effects of different 'treatments' on a single 'individual' over time. The single 'individual' could be one person or a group acting as a ...
30
votes
5answers
6k views

Strategies for teaching the sampling distribution

The tl;dr version What successful strategies do you employ to teach the sampling distribution (of a sample mean, for example) at an introductory undergraduate level? The background In September I'll ...
6
votes
2answers
2k views

CART (rpart) balanced vs. unbalanced dataset

I am fitting a tree (CART) to the olives-dataset. The training data has 436 observations (test data: 136). I have 3 responses (the 'Region' variable) which splits the training data into 116 / 74 / 246 ...
4
votes
1answer
1k views

Resources about forecasting stock returns with SVR

I'm currently working on SVR to predict stock market returns and I would like to know if anyone of you could give me some advise regarding interesting papers on it. These are the articles I'm ...
3
votes
1answer
4k views

k-fold cross-validation strategy for large data set in statistical learning

I'm trying to learn the Bayesian network structure from a very large data set, and the R package I used for learning can only handle a very small portion of the data set (~10%) at one time due to the ...
2
votes
2answers
188 views

Determine range that contains given ratio of data points

I'd like to determine the "representative" range for a series of data points. For example, I'd like to know the range where 98% (or any other given ratio) of points are located. I could have used the ...
5
votes
1answer
4k views

What kinds of variables should we use the normality test for?

When should we apply normality tests? For which types of the variables should we apply the normality test? For example dependent variables, independent variables, or control variables, etc?
3
votes
2answers
5k views

Are composite variables (eg. a score) valid to perfom a SEM in AMOS?

I have a resilience scale with 11 items (observed variables), from which I calculated the mean to get a "resilience score" (what would usually be an unobserved variable or latent construct in SEM ...
4
votes
1answer
510 views

Repeated measures ANOVAs instead of repeated measures MANOVA w/ small N?

I have 3 variables that have been measured on 4 occasions and a sample size of 16. I was considering a repeated measures MANOVA to ascertain if the changes over time were statistically significant. ...
2
votes
1answer
147 views

Method to classify and recode high and low probability regions?

Most classification methods typically train and predict over all instances, possibly giving a less efficient answer. To give an example, imagine two randomly populated regions on a 2D grid (both ...
2
votes
1answer
490 views

Attempting to define linear weights for Goals scored in the English Premiership

I'm very keen on sports and am just starting to understand how I can start to apply maths to sports related problems and issues. I'm keen to get some pointers in the right direction for the linear ...
16
votes
3answers
33k views

What does Theta mean?

I am a newbie to statistics and found this. In statistics, θ, the lowercase Greek letter 'theta', is the usual name for a (vector of) parameter(s) of some general probability distribution. A ...
2
votes
2answers
310 views

Best way to go about correcting for multiple comparisons (or should one even) for a small dataset?

Disclaimer: I have a very minimal stats background and am just getting into this stuff. Corrections to any terminology I use or an improved rephrasing would be super appreciated. I have a simple ...
8
votes
1answer
202 views

Which distributions on [0,1] other than the beta distribution form nice compounds with the binomial distribution?

For which distributions x, other than beta, is the x-binomial distribution nice? The beta and binomial distributions are famously conjugate but I am curious if other non-conjugate distributions will ...
1
vote
1answer
140 views

What test should i perform?

I have a questionnaire with a five point scale. Differences in means is obtained. As my data is not normal I am using NON-PARAMETRIC tests for my comparisons. Population: 1 group (Pharmacists only) ...
1
vote
1answer
164 views

Could anyone identify this book?

I am trying to find a book I once partially read without much luck. The book's main topic, if I remember right, is stochastic processes. It was, I think, a not too heavy blue/light blue book. The ...
0
votes
0answers
1k views

Overdispersion in GLMM in SPSS

I am using a generalized linear mixed model to analyze poisson and binary data. Animals were observed on several moments, so my model should account for that, which is why I am using the GLMM. I am ...
4
votes
1answer
168 views

Distribution of atan2 of normal r.v.'s

Given $X\sim{\cal N}(\mu_X,\sigma^2_X)$, $Y\sim{\cal N}(\mu_Y,\sigma^2_Y)$ I am looking for the p.d.f. of $\operatorname{atan2}(Y,X)$ where $\operatorname{atan2}()$ is the 4-quadrant arc tangent. Does ...
1
vote
0answers
216 views

Hypothesis test for difference between domain means with weighted data

I have a large dataset that is weighted due to: probability proportional to size sampling, & disproportionate stratification. I would like to compare the means for two different domains ...
1
vote
0answers
312 views

Changing reference level on mixed model changes pMCMC value

I'm using an lmer on a set of continuous data. This post helped me a great deal when interpreting results, as I have two conditions and three levels as well, but I've run into a frustrating problem. ...
12
votes
2answers
1k views

How to estimate the third quartile of binned data?

Is there any technical trick to determine the third quartile if it belongs to an open interval which contains more that one fourth of the population (so I can't close the interval and use the standard ...
0
votes
2answers
124 views

What type of model makes sense?

I am looking to model physical activity (in minutes) as my dependent variable. I have several independent variables of the environment around the school (intersections, traffic, etc). What type of ...
2
votes
0answers
207 views

What is the name of the distribution whose support is (0,1) and whose pdf kernel is exp(ax) - 1?

Does this probability distribution have a name? $$f_a(x) dx = \frac{a}{e^a-(a+1)} \left(e^{a x} - 1\right) dx, \quad 0 \le x \le 1.$$ Edit: I want $a$ to be positive. I don't think this is what is ...
2
votes
1answer
2k views

Should I keep or remove random effects?

After attempting to produce a linear mixed model, I was left with a great deal of heterogeneity. ...
4
votes
2answers
447 views

Is repeated measures ANOVA a correct method for my data?

My experiment is a completely randomized block design. The objective is to find whether a variable is different between species $a$, $b$, $c$. The measurement was taken 2 times (June, July) in each ...
2
votes
1answer
3k views

About the usage of CATPCA

I have some questions regarding the usage of CATPCA in SPSS. I hope the answers to these questions will be helpful for others too who are planning to work on it. 1) In my data (on this data I want to ...
5
votes
1answer
659 views

Edge correction of Ripley's K-function for two 1D point processes?

I am just beginng an investigation involving characterizing the dependence between two 1D stochastic point processes $x$, $y$. The natural approach seems to involve Ripley's K-function: $$ K(t) = \...

15 30 50 per page