# All Questions

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### Is it possible to use WEKA in a web based application? [on hold]

I am building a web based text mining application. For a word that user enters, the application has to: search it in google gather the documents pre-process by using Bag of words model cluster ...
27 views

### Simulation & statistical distribution

Can you still use simulation techniques if you do not know about the statistical distribution of the population under study?
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### multivariate logistic regression

I have a quick question. I wondering to know, whether there is a step by step guide to learn multivariate logistic regression. i have a health science paper which described the procedure, but it is a ...
16 views

### Segmented Regression With Control Group Implementation and Interpretation

I have been reading the following paper on segmented regression for interrupted time series - Wagner 2002 and wanted to learn a proper analysis of such data where there is a control group. The paper ...
40 views

### cross-validation: what is the standard deviation if the same value is obtained for each fold?

Here is a detailed imaginary example: I am using 5-fold cross-validation to estimate the generalization MSE of my predictive model. When I hold-out fold number 1, which contains 10 observations, say ...
18 views

### Constraining coefficients in linear regression

I am trying to estimate a model of how rail freight shipping rates are effected by a number of different variables, including the price of fuel. There is such little variation in the price data that ...
29 views

### Binomial Distribution With Scale Variable?

I'm attempting to generate some random data using a distribution. I need each random point to fall within a certain range e.g. 0-20, and I would also like to control where the center of the curve ...
31 views

### Forecasting - Population Death Rates

Wondering if you can help me out with this problem: I have 2 closed populations of products (call it Product X, and Product Y). Population Size of each product 10 million each (Product X = 10 ...
18 views

### Partial Least Squares regression

Assume we have a simple linear regression model expressed as $Y= X \beta + e$, where $Y$ is a vector of size $n \times 1$, $X$ is a matrix of size $n \times p$, $\beta$ is the regression coefficients ...
94 views

### Monty Hall (goat) problem w. elementary events

I am trying to solve the Monty Hall problem with elementary events, but I just can't seem to get it right: I define four sets: Actual door ($R$) User's first selected door ($S$) Moderator pick ...
24 views

### Three Different Regression Results… Why is one so weak compared to the other two?

I have a data set I'm working with, it's roughly 450K rows of data. I'm breaking the data out from a certain column, and that column has three results. After that, I ran a regression analysis for each ...
8 views

### Structural partition for cross validation

Can the partitioning of data for cross validation be used structurally to assess the transfer ability of an effect of one factor across another factor? A MANOVA performed on multivariate data reveals ...
15 views

### Meaning of large values of parameter b (|b| >>) 4 in IRT theory

I'm working with a set of data from a 100 itens, 5 alternatives, medicine test and analyzing them by means of IRT (. The IRT - 3 parameter model yielded some values of b that are very large (...
8 views

### Naming of a Function which Estimates Other

Sometimes we can’t optimize a function (or objective) itself (e.g. because of complexity), and thus we try to optimize another function (or objective) that is similar to it. I think there was a name ...
14 views

### Testing a single time-series for changing variance structure (Heteroscedasticity and Volatility Clustering)

I would like to assess a single time-series for a changing variance structure that might be leading to spurious variance estimates when that time-series is used in regression. In my head two terms ...
46 views

### $\log[E(y|x)]$ vs $E[\log(y)|x)]$

I have these two equations for elasticity: $$\frac {∂\log[\hat E(y|\mathbf X)]}{∂\log(\mathbf X_j)}$$ & $$\frac {∂[\hat E(\log(y)|\mathbf X)]}{∂\log(\mathbf X_j)}$$ I understand that if my ...
16 views

### R for lme complicated study design

I have a data set where siblings (brothers and sisters) had the quantity of a specific bacteria measured at specific intervals since their birth (2 weeks, 1 month, 2 months, 6 months, 1 year). Because ...
19 views

### Removing outliers for a more “realistic” linear programming formulation

For the past two school quarters I have been collecting data on my study habits. I would like to use this data to formulate a linear program so that I may optimize my study time. The first quarter I ...
31 views

### Does sampling from a larger sample change how much variance around an estimate to expect?

Suppose you have one billion marbles. Each marble is either red or white. Call the proportion that are red, p. You randomly sample 100 marbles. Based on this sample you estimate $\hat{p}$. You can ...
12 views

### User engagement ranking algorithm

Really short problem description: users earn "points" for different actions in the online application. Each action earns different amount of points, based on how "important" action was (creating ...
3 views

### Changing polynomial degrees leads to different coefficients in Fuzzy RDD

I am running a Fuzzy RDD and I am getting some unusual results, the coefficient of interest changes sign and significance with different polynomial specifications. When using a linear polynomial ...
4 views

### Compare samples when each “object” of the sample is a success rate [0,1]

(I don't have a STATS background) I have two samples of different sizes (around 100) A = {0.1, 0.2, 0.21, 0.42, 0.56, 0.32, 0, 0,...} B = {0.943, 1, 0.56, 1, 0.86 ... } each element/object of A and ...
19 views

### Help understanding a kriging variation for bare earth extraction

Problem: The authors of a paper (http://www.isprs.org/proceedings/XXXIV/part3/papers/paper106.pdf) develop a bare earth extraction algorithm for LiDAR that is based on kriging. What I don't ...
13 views

### Interpretation of odds ratio in logistic regression

In the study of birth weight (low or normal) of a child, the "birth term" of the child has been considered as a risk factor. The birth term has two categories: premature and full-mature.The following ...
11 views

### Correct handling of compound covariates in glmnet()

Cross Validated list-serv followers: I should like to hear your thoughts with respect to the issue of how composite variables should be handled in glmnet(). This issue does not relate strictly to ...
34 views

### How to generate the posterior predictive distribution for hierarchal model in PYMC3

See iPython notebook for full example The below stochastic node y_pred enables me to generate the posterior predictive distribution: ...
8 views

### R - cor.ci results interpretation

I am doing some survey analysis for my dissertation, and am interested in studying possible correlations between four variables, based on Technology Acceptance Model.The survey is built on a ...
12 views

### Clustering without multiple variables

I want to cluster a set of schools according to their academic performance (using the marks of students from each school for a special exam). But the data set only contains the name of each school and ...
14 views

### Deviance explained in classification randomForest model?

Is there a way to estimate deviance (or variance) explained from a classification model in randomForest? I've seen "deviance remaining" reported for presence-absence random forests in the SDM ...
16 views

### association between discrete variables and continuous variable

I am having little difficulty with understanding the difference between, testing association between two variables and modelling them. Say I have binary outcome x(sold, not sold), and i have all ...
23 views

### Cost function spiking upon using dropout on neural network

Upon using the dropout technique, my cost function is spiking arbitrarily. Is this normal? If not, how do I avoid it? I'm using a salt-and-pepper mask to drop out neurons at a dropout rate of 5%. ...
17 views

### Could Use Assistance On A Work Project [on hold]

This might be a little unorthodox, but I could use some assistance on a work project. I work for a small company. We don't have any formal data sciences or analytics department. I was tasked with a ...
100 views

### Is there a non-parametric Coefficient of Variation?

I was reading a paper where the author mentions: "The coefficient of variation is primarily a descriptive statistic, but it is amenable to statistical inferences such as null hypothesis testing or ...
13 views

### Statistical test to show if there's significant statistical difference in a set of outcomes

I am trying to find out if there's statistical difference between a set of outcomes. The event involves potting snooker balls; here are six students, each of them is required to pot 10 snooker balls, ...
8 views

### How to check stability condition of VEC estimates in R?

I am estimating a VEC model and need to check the stability of its parameters. The vars package has a function to do this on an object of class varest generated by ...
15 views

### Running factor analysis for pre and post-tests

I don't know if I can combine the pre and post-tests data and then run an exploratory factor analysis (EFA). Here is what I did: 50 participants took a pre-test and then post-test after one month. ...
12 views

### DCCA clustering algorithm understanding

I try to understand the step 2.5 of the DCCA clustering algorithm pasted below. The original reference is here and the PowerPoint presentation is here. I have the following questions: Do we perform ...
16 views

### modeling sales based on different quantitative and qualitative variables

I'm new to machine learning and am interested in being able to try different modeling approaches to find the model that will predict future sales the best without overfitting/overtraining. I have been ...
11 views

### Improving estimates of linear system regression when parameters are unevenly weighted

I have a system with a linear model $ax + by = c$. I can adjust $a,b$, measure $c$ (with some error in the measurement) and then use linear regression to estimate $x,y$. The problem I'm running into ...
33 views

### Rare event logistic regression bias: minimal example

CrossValidated has several questions on when and how to apply the rare event bias correction by King and Zeng (2001). I am looking for something different: a minimal simulation-based demonstration ...
14 views

### Relationship between Poisson arrival rate and Exponential inter-arrival rate

A poisson distribution has a lambda 1.5 per minute. I would like to know as to how would i use this for the lambda in exponential distribution? Would both the lambda values be the same?
22 views

### what is the intuition behind the SRSWOR formula?

I earlier asked about Slovin's Formula (http://math.stackexchange.com/questions/1410492/what-is-the-intuition-behind-slovins-formula), and learned shortly thereafter that it was derived from this ...
26 views

### Lagrangian multiplier: role of the constraint sign

I am beginner learning Lagrange multipliers with wiki article. Consider: maximize $f(x,y)$ subject to $g(x,y) = 0$ I understand that to maximize I must follow the gradient $\nabla {_{x, y}}^{}f$. I ...
21 views

### Multiple continuous observations in HMM gaussian mixture

I am building a hmm which emits 3 types of continuous observations. I intend to model each observation sequence as a vector in $R^3$. I am new to hmm and my first question is can I use a tuple or ...
22 views

### Confused about hypothesis testing, tails, and confidence intervals

$Y_1, \ldots, Y_{10}$ are $N(\mu, \sigma)$ random variables. We observe $\overline{Y} = 20$ and a standard deviation of $1.265$. We are asked for a $95$% confidence interval. Use the t-table, we find ...
18 views

### Different output for cox regression in R vs SPSS

During my analysis that I perform with a collaborator we get consistently different ouputs in cox regression between R and SPSS. Betas and p-values differ minutely, usually somewhere in the third or ...
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### Confidence intervals for Tobit model in package AER in R

I use a Tobit model to predict censored data. I use the AER package in R. A toy example looks as follows: ...