# All Questions

37 views

### Model Formulae. correct model?

I'm trying to build the following model in R, however I'm quite confused about the model formulae to use to include an interaction (x1 and x2) $Y_{}=a+b*x_1+cx_2+d(x_1*x_2)$ this intuitive formula ...
33 views

### Generate data from a bivariate power-law distribution in R

I need to generate data from a random vector that follows a bivariate power-law: $$f_{X,Y}(x,y) = \frac{C}{XY} \left(\frac{X}{X_0} \right)^{-\alpha} \left(\frac{Y}{Y_0} \right)^{-\beta} ,$$ where ...
26 views

### Can we find the Hazard Time by using Cox PH model for give covarites?

Can we find the Hazard Time by using Cox PH model for give covarites? I have built Cox PH model using the following equation. cph1=coxph(Y~tx+age+strat2) My output is ...
22 views

### What's the optimal way to encode a 'month' feature? [on hold]

What's the optimal way to encode a 'month' feature? A single integer value or 12 binary values don't quite grasp the concept of modulo distance... Say I want to train an SVM for a certain task and ...
28 views

### Visualize process data

I have a dataset of order processing with 8 million rows with following columns: HistoryId - Identity column of the records ...
24 views

### Repeated measures vs. cluster in logistic regression

I have data from an experiment in which participants played a repeated game 50 times. That is, I have 50 data points per participant. I want to run a logistic regression and I have of course to take ...
7 views

### calling weka classifier with crossvalidation in matlab [on hold]

how can we call weka classifier in matlab with cross validation? weka.classifier.evaluation.crossvalidatemodel() what parameters we can pass to crossvalidatemodel in matlab
103 views

### High precision with low recall SVM

I'm classifying a data set using SVM and those are the precision and recall values for two classes. ...
13 views

### mixed model vs. markov chain

I have a longitudinal data with multiple time points (measured twice every year). There was seasonal difference on the outcome variable of interest (BMIz) if using mixed model (where time points were ...
13 views

### Error in eval(expr, envir, enclos) : object 'Case' not found in train( method=rpart) in caret package of R [on hold]

I am trying to fit my training data for Coursera Practical Machine Learning Quiz 2. ...
32 views

### Random Forest: Important variables, Important values

I've been reading up on random forests and have come to a stumbling block in regard to their practical application (an probably fundamental understanding). This problem i in regard to important ...
49 views

### Kruskal–Wallis Test not significant but Mann Whitney U significant

I have a non-normalized dependent variable and an independent variable broken down into 4 groups. As such, I used the Kruskal–Wallis analysis to look for significant differences in the ranks of the ...
26 views

### What Statistical method is necessary to determine the correlation amongst a set of individual correlations? [on hold]

I have a question regarding the statistical method necessary to determine a correlation between a set of individual correlations. Below is an example of a situational question I currently face. There ...
19 views

### inference Single sample [on hold]

Can someone Answer this question. Thanks in advance. 6.17 the one with black circle. Right now i have no idea how to approach and solve it.Any help would be highly appreciated. Thanks.
16 views

### Experimental design and mixed models

I want to test effect of 3 PH on larval development. I would like to know what is the best experimental design and statistical analysis. We can only use 3 compartments of sea water, each one with a ...
16 views

### SVM Classification with Duplicate Training Instances

I'm using SVMs with linear kernel for sentence classification (binary). My dataset contains many duplicate instances i.e. many sentences in the training set have identical feature vectors. In the ...
11 views

### Unbiased Estimator of Days Until Completion?

I'm trying to get an estimate of average number of days until some event occurs (the event is guaranteed to eventually occur). I have some sample where this event has already occured for most ...
30 views

### How to plot a comparison of read counts in R

I have a bunch of genetic read counts for different several genes. Each gene is divided into two groups (0 and 1). What I want to do is make a vertical plot side by side of the 0 group and the 1 ...
22 views

### Statistical Significance or Unambiguous Direction of Influence?

With this post I want to put forward an interpretation of the concept of "Statistical Significance" in the context of "frequentist" Hypothesis testing that rings very convincing to my ears. I am not ...
12 views

### Seeking covariates that can negate the effect size of treatment groups in an ANCOVA model

I was going to build an ANCOVA model with two treatment groups (climbed/unclimbed) and a set of 10 potential environmental covariates which may collectively remove the significance of the climbing ...
16 views

### What is the superior strategy in opening cells here?

This is a problem I just completed for a quiz online. Was wondering if someone could help me reason this out. Suppose you receive a message and you are trying to decide whether Team Rocket or Team ...
33 views

### What are the null and alternate hypotheses? Will you use a left, right, or two-tailed test?

Ben has a coin which he claims is weighted in a way so that when he flips it, heads appears more often than 50% of the time. He tries to prove it to you by flipping the coin 100 times, which ...
9 views

### Binary classification with too few positive samples

I met a problem of doing a binary classification with quite few positive samples. For example: Binary classification with either labelled 1 samples (positive) or labelled 0 samples (negative ...
10 views

### calculate mean for groups [migrated]

I'm doing a research about SATs scores by cities. I have every city coded. Is there any way to ask stata to calculate the mean for each city without having to type the city-code? Not having to write: ...
13 views

### Combining data sets that have been adjusted for multiple testing

I have what I think is a simple question. Let say I have 5 data sets with with a variable number of tests (say 1-10K) and I control the FDR in each set to 1% using BH. If I combine these BH ...
26 views

### Is LDA more likely to be overfitted than SVM?

I went to a short talk and the speaker quickly mentioned something like 'LDA is more likely to be overfitted than SVM'. Is this true? And why? Thanks a lot. A.
13 views

### How many features can be used for classification?

Asked a similar question the other day without an answer Link. I think maybe the question there is too big. Here I want to ask a specific one: 2 Class labels (Binary classification labelled with ...
21 views

### How to evaluate a statistical test for fairness of a coin?

I suspect that a given coin is not fair, i.e that the probability of heads is not $\frac{1}{2}$. My question is not how we can prove the unfairness, but if we derive a test to check the fairness, How ...
19 views

### Arima model - multi step forecast

The following code shows a forecast of the next 24 hours of my electricity prices with two exogenous variables. My problem is, that I don't know how to build a forecast for the next 3 days or more ...
8 views

### Is there an effect size for Kappa's?

I am staring a project on comparing standard ways of creating a classifier with some heuristic methods. The heuristic methods should result in a faster training for the classifier but should result in ...
41 views

### In confusion with a Bayesian statistical problem

I was learning some probability basics. I am stuck with a problem, that I need your help with in solving. An $e$-fair coin is a coin with probability of head $(\theta)$ in interval ...
6 views

### Modification of categorical outcomes in small samples

I have a set of abnormal lab findings and a set of tenderness outcomes in a small sample of "cases" and "positive controls". We hypothesize there may be some lab findings which differentially affect ...
36 views

### Seeking a continuous, parametric, bimodal sampling distribution for proportions

I am seeking a parametric probability model whose pdf has the following characteristics: (1) it is supported on a variate axis that is bounded between 0 and 1; (2) it is continuous; and (3) it is ...
8 views

### Utilizing A Correlation Matrix Derived from a Sparse Matrix

I have large correlation matrix in Excel that I'd like to use to inform my choice of explanatory variables in a multiple linear regression model. One problem is that the initial data was very sparse, ...
458 views

### Why does frequentist hypothesis testing become biased towards rejecting the null hypothesis with sufficiently large samples?

I was just reading this article on the Bayes factor for a completely unrelated problem when I stumbled upon this passage Hypothesis testing with Bayes factors is more robust than frequentist ...
35 views

### Lower and Upper confidence limit on estimated arithmetic mean using Land's exact

I have to compute the LCL95% and UCL95% using Land's "exact" method. I computed the LCL and UCL for this lognormal distribution using another technique and I cant find anything for Land's Exact ...
55 views

### Should a Poisson regression be carried out with only 3 data points?

I'm trying to test the relationship between the number of adults counted and the percentage heather cover over 3 areas. The data looks like this: ...
12 views

### How to compare the nested models which each of them comes from diffrent dataset?

I have four nested models.Every of them learned from different data sets. now I want to compare these models together.normally people try to compute the F-satistics. But for my case, it's bit harder, ...
27 views

### Significance of varibles after stepwise regression

I did stepwise regression with my multiple regression model and using AIC as a measure of fit with the step function in R. Afterwards some variables that the ...
13 views

### Difference between Factorization machines and Matrix Factorization?

I came across the term Factorization Machines in recommender systems. I know what Matrix Factorization is for recommender systems but never heard of Factorization Machines. So what's the difference?
17 views

### Partition of sums of squares (ANOVA)

Can anyone explain the theory (or the formula) about computing Sum Sq (bold highligh below) related to regression items? The Wikipedia link gives an introduction on how to calculate the total, model, ...
20 views

### What is the plim estimator of $\beta$, What would we need to obtain a consistent estimator of $\beta$?

Suppose that the true model is $$Y_i = βZ_i + u_i$$ However, the researcher/analyst can only observe $X = Z + w$, where $w$ is a measurement error with zero mean and constant variance $\sigma^2_w$. ...
59 views

### Basic problem in Bayesian inference

I have questions with the following Bayesian inference problem I found in the book by Bertsekas & Tsitsiklis (Introduction to Probability 2nd ed.). Problem is as follows (P.445, Problem 2): ...
21 views

### T-Tests and Regressions

my supervisor has asked me a few questions that I'm not entirely sure how to answer. For a quick summary, my study includes a small sample of 16. To describe the sample, I compared the scores of the ...
18 views

### Variance of parameters

I have three estimated parameters, $\hat{\beta_0}$,$\hat{\beta_1}$ and $\hat{\beta_2}$, these follow the ordering $\hat{\beta_1}\leq\hat{\beta_0}\leq\hat{\beta_1}$, where these parameters are ...
25 views

### What is a semantic map

Based on: J. P. Carvalho, "On the Semantics and the Use of Fuzzy Cognitive Maps in Social Sciences" (WCCI, 2010 -- PDF) and Richard Dagan's web page Cognitive Mapping. A cognitive map consists of ...
13 views

### Simulated MLE does not exist, when trying to Bootstrap likelihood combinant

Consider this simple logistic model: We have ten $0/1$ observations $y_1,...,y_{10}.$ We model with an intercept and a predictor variable.The ten first observations have predictor value $X_i=0$, ...
17 views

### Holt Winters Initialization Issue

I am using an additive seasonal Holt-Winters model to compute confidence band of my data. I followed the HW initialization process described by Rob J Hyn­d­man. The confidence band is derived by ...