# All Questions

3 views

### Translate exponential formula into excel

I am having difficulty converting an exponential formula into one that can be used in an Excel cell. If someone can help me convert the following formula that would be a huge help: y = ...
4 views

### How to choose between poisson regression and zero inflated models

I have data on children visiting the A&E department. I want to see which variables are associated with the numbers of visits. For instance, if genetic factors are associated with more visits to ...
2 views

### How to define a subset with proper mathematical notation

My question is related to set notation. How can I differentiate with proper mathematical notation between the following 2 subset selection approaches? From an initial set ...
3 views

### How can an artificial neural network ANN, be used for unsupervised clustering?

I understand how an artificial neural network (ANN), can be trained in a supervised manner using backpropogation to improve the fitting by decreasing the error in ...
21 views

### Loss function from Posterior log likelihood

I am trying to implement Bayesian Logistic Regression and was looking at this paper http://www.stat.columbia.edu/~madigan/PAPERS/techno.pdf. The authors in this paper had assumed the $\beta$s to have ...
5 views

### STL + Random walk failing

We have four months of data (10 minute interval), this seems have nice pattern (at least for eye ball). We are using STL to decompose the time series and apply "random walk" to project next month ...
11 views

### Neuralnet function error in R [on hold]

I try to run neuralnet() in R, which have response variable as diabetes (categorical) as function of 8 predictors (with one ...
184 views

### Significance of variance components in Stata output

This might be trivial, but I'm used to HLM7 software output and now I'm switching to Stata (xtmixed). To give an example imagine I have students (level-1) nested ...
1 views

### What is an “example based” metric?

In the context of multilabel learning I came across several "example based" metrics, for instance example based Recall, example based Precision etc. (see here) I do know the concept of Recall etc. ...
79 views

### Metric to compute structural similarity between two directed graphs

I'm working on a small project in which I try to compare directed a-cyclic graphs. Say I have (directed) three graphs: 1) ...
5 views

### Maximum Entropy with no index

This is a simpler problem than trying to solve, but have a feeling once get the methodology I can apply it to the harder problem. Let $H(p)= -q \ln(q) - p \ln(p)$ be the entropy of the Bernoulli ...
78 views

### Some basic questions related to the moments of a probability distribution

The available text books in most cases avoid greater details regarding some of the topics related to the moments of a probability distribution and I feel some of those topics are not really clear to ...
23 views

### Which variables to keep in my analysis based on loadings from PCA?

Could someone please explain me how I should decide which variables to keep in my analysis based on loadings from PCA. The output is: ...
72 views

### Tricky Poisson distribution question

Am new to probability and have been struggling to solve the following question. Assume $X_1, \ldots,X_4$ are IID with $X_i ∼ \text{Po}(λ)$. Let $Y = \frac{1}{4} (X_1 + \ldots + X_4)$. Find ...
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### combining a random variable and its inverse

I am measuring two scientific entities, X and Y using empiric measurements. Each has its own mean and sample variance based on Nx and Ny sample measurements. I know from the underlying science that X ...
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### Departures from normality in factorial design

This paper (http://psycnet.apa.org/journals/med/6/4/147/) states that departures from normality can be tolerated for one-way ANOVA. "The results give strong support for the robustness of the ...
3 views

### Association Rule with Quantity / Number of Items

Normally, Association Rule can mine rules such as {butter, milk} => {bread}, but it only looks at whether or not butter and milk are bought together, not the quantity of each item bought. For example, ...
10k views

Recently, I have found in a paper a statement that p-values should be uniformly distributed. I believe the authors, but cannot understand why it is so.
18 views

### Hypothesis testing for seasonality

i want to make hypothesis test for a data for pH values measured for each month of a year. I want to test whether there is any correlation ie: are the values for month of summer having similar values ...
13 views

### Online Panel For Survey - Can It Be Representative?

I am thinking of using a company that has an online panel to recruit participants for a questionnaire study. Because the demographics (age, gender, region etc) of the entire population is known ...
6 views

### Change Point Analysis for Environmental Data

Does anyone know of somewhere with resources on using change point analysis for determining environmental threshold values? Let me emphasize that this is NOT time series data. Change point analysis is ...
7 views

### Bivariate gamma distribution with one parameter marginal

the marginal distributions from a joint gamma distribution seems to always contain two parameters in each marginal. For empirical purposes, normalization is needed so that the shape and scale ...
44 views

### How to document a Random Forest result (final model)?

Using Random Forest to predict dichotomous variables (for classification) I encountered the problem how to best document this model, i.e. I want the user to reproduce/use the final model I created on ...
25 views

### Question with Copulas

I've come across this question in my class which I'm struggling with. If we have the copula $C(u_1,u_2)=\phi^{-1}(\phi(u_1)+\phi(u_2))$ where $\phi(u) = (-\ln (u))^{\gamma}$ for ${\gamma} \ge 1$, ...
7 views

### Comparing two distribution known by their deciles

I am trying to compare a travel time measuring device with a reference device. The assessed device only provide the decile (+min and max values) and not all the measured individual travel time. I am ...
38 views

### About a problem of R in Linux [on hold]

When I use Rscript xxx.r to run a R script in Linux, I found that if I run it twice, the variables I used in the first time will not be kept when running the second ...
4k views

### Log-linear regression vs. logistic regression

Can anyone provide a clear list of differences between log-linear regression and logistic regression? I understand the former is a simple linear regression model but I am not clear on when each ...
56 views

### What is the reason for this discrepancy between confidence level and probability?

I ran the following R code: library(Hmisc) binconf(x=1, n=70) # PointEst Lower Upper # 0.01428571 0.0007327613 0.07658187 Which is the ...
55 views

### Fitted model of linear spline regression in R

If the linear model is fitted as follows, what is the formula of the fitted model? I need to use the coefficients outside R. ...
811 views

### Gaussian Ratio Distribution: Derivatives wrt underlying $\mu$'s and $\sigma^2$s

I'm working with two independent normal distributions $X$ and $Y$, with means $\mu_x$ and $\mu_y$ and variances $\sigma^2_x$ and $\sigma^2_y$. I'm interested in the distribution of their ratio ...
14 views

### How to use the r package to compare different models on 10-fold CV [on hold]

I want to compare the classification performances of 5 different models on 21 datasets using caret with 10-fold CV. I have read the manual and examples and was wondering whether the package is ...
21 views

### preferential multinomial model (with memory)

I am modeling a system that is like having a container of an infinite number of colored balls. On each day $t$, I pull out a new set of $n_t$ balls and I count the number of balls that are red, green, ...
9 views

### Double Repeated Measures in SAS

Given: main effects A 2 levels urban, rurual F 17 families- 10 urban, 7 rural repeated measures ...
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### SAS Enterprise Miner, BINARY versus Interval variable predictors [on hold]

I am doing a logistic regression in SAS Enterprise Miner, of a response variable with a bunch of predictors. Once of the predictors is age_cat (0/1), age_cat = 1 if (age < something) 0 otherwise. ...
67 views

### Approach and example of graph clustering in “R”

I am looking to group/merge nodes in a graph using graph clustering in 'r'. Here is a stunningly toy variation of my problem. There are two "clusters" There is a "bridge" connecting the clusters ...
8k views

### What's a real-world example of “overfitting”?

I kind of understand what "overfitting" means, but I need help as to how to come up with a real-world example that applies to overfitting.
359 views

### Tutorial for performing Contrasts for MANOVA

Context I have a multivariate dataset with a test group and three control groups. I was thinking that the best way to determine if and how the test group differed from all of the control groups would ...
4 views

### Distribution of test statistic in ARCH LM test

To test for ARCH effects in a time series, there is the ARCH LM test. Its test statistic is $\chi^2(n)$-distributed, where $n$ is the number of lags in the test regression. But if you have run ...
9 views

### Durbin Watson test

Can we use Durbin Watson test to test autocorrelation in time series data ? I want to find if values of pH in water measured for each month of a year have seasonality. More precisely whether they ...
9 views

### getting fitted lines with scatterplot matrix in r [migrated]

How do I get a scatterplot matrix which will also show the fitted lines in each plot. I know how to use "abline" function with individual plots but don't know how to implement it in a scatterplot ...
23 views

### Derive the Gibbs sampler for this bivariate distribution

I understand the theory of Gibbs sampling. It is an iterative sampling algorithm that defines, sequence of random variables with the property of a Markov chain. Specifically, I choose any starting ...
3 views

### Specifying model type in R package eHOF [migrated]

I can't figure out how to specify the model type in package eHOF (I want to plot a model other than the one chosen by the program). I create a HOF object: ...
12 views

### using biomod2 package with continuous response variables

I am looking to correlate crop area with climate variables and then predict for future if suitability of crop areas will change/remain same under different climate scenarios (in line with species ...
169 views

### Data analysis: Time series for Bacterial population data

Could anyone please help with data analysis. Briefly, I am studying how the population of a bacteria changes at different points (port 1 to port 10) within a biofilter over the course of 30 days(like ...
19 views

### Can regularization path reveal collinearity?

I know that the penalized Regression is robust to collinearity. I also found a page at scikit-learn : Plot Ridge coefficients as a function of the regularization says it "shows the effect of ...
19 views

### Is the difference in risk statistically significant?

I performed propensity score matching and thus generated a quasi-randomized study. No I got a risk for Akute Kidney Injury of Drug1: 15.6 % Drug 2: 11.2 % Sample size = 4711 control + 4711 treated ...
10 views

### Neural networks: Active input range of activation functions?

I'm playing with the Neural Network toolbox in MATLAB. I've noted that each activation function (aka, transfer function) has 2 properties: the output range, which, if I understand, is the codomain ...
162 views

### kozachenko-leonenko entropy estimation

I'm trying to implement the entropy estimation based on the closest neighbour from Kozachenko and Leonenko but I'm facing a problem I can't solve. The idea is to work in a new set ...
My situation is as follows: I want, through a Monte-Carlo study, to compare $p$-values of two different tests for statistical significance of an estimated parameter (null is "no effect - parameter is ...