# All Questions

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### Binary logistic regression in R - assistance with determining odds of a predictor at different levels

I have performed a binary logistic regression in R with whether or not a sportsperson was re-contracted or not as the DV. My final model is as follows; ...
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### What should be the correct result of this product $(Y-XW)^T(Y-XW)$

i usually come across this equation and I am not able to understand it entirely, here X, W and Y are matrices of size N*D, D*1, and N*1 resp. $(Y-XW)^T(Y-XW)$. As per me it should be equal to ...
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### probability of side A in tossing 3 times of 4-sided dice

Q: Find the probability of one side (let's call it A) showing up at least once in three tosses of a 4-sided dice. I get different answer if I do 1-P(no A's) versus P(one A) + P(two A's) + P(three ...
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### Tool for implementing neural networks

I am doing a project on offline signature verification (not classification) using artificial neural networks. Which tool/api should i use? Also mention the options i have with their strengths.
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### Random effects in GAM

I am now trying to use random effects in GAMs developed by Professor Simon Wood. Prof Wood uses s(...,bs="re") to account for the random effects. Random intercepts models or random slopes models are ...
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### pdf estimation in R - np package [on hold]

I need to nonparametrically estimate a pdf in R (I'm using the np package which works great!), and I have the problem that the support of the distribution is finite, so the estimator is biased close ...
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### How to calculate the probability that a scalar data point maps to a class?

Suppose that I have the following data set that maps students' test score to the class in which the student belongs: ...
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### Combining different normality transformations for Fisher's method

I have 2 data sets that are applicable to Fisher's method. One has a p-value of 0.07 and the other 0.15. Neither sets were normal or homoscedastic. The first satisfied the ANOVA assumptions only with ...
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### How can I approximate a pdf knowing the estimated CDF in R?

I have an estimate of a CDF in R (nonparametric) and I need to compare this distribution to another one by Kullback-Leibler. In order to do so, I need to find the pdf of this random variable. What is ...
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### What are the recent real life use or applications of the Cauchy Random Variable?

We have a short assignment on the described question and I already have gone through a lot of trash results from Google. I can't seem to find any. I don't know where else to post this question. ...
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### Multiple time series - class of problem with agents and events?

I'm working on a prediction problem and struggling to find applicable resources (articles, tutorials, papers) that address this class of problem. I'm assuming the info is out there and I'd love to ...
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### Comparing classification accuracies with different numbers of features

I have a classification problem in which I’m trying to assign a label to each of a collection of inputs x_i. I’m comparing two different feature representations of the inputs, trying to determine ...
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### Are all right skewed distributions the result of a multiplicative process?

If log normal distributions are the result of a multiplicative process and right skewed distributions become normal once converted to logs (i.e. are log normal). Then, can one generalize and say that ...
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### Results from fractional polynomial models

I am using multivariable fractional polynomials to evaluate several continuous variables in a Cox proportional hazards model. I have the beta coefficients, however, I would like to estimate the hazard ...
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### Poker chance of straight draw on the flop from connectors 34 - TJ

Poker - 52 cards 4 suits of 13 (rank) cards each Poker probability Rank - ace (1) is both high and low so A23456789TJQKA A straight is 5 sequential cards A flush is 5 cards of the same suit ...
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### Using glmnet/lasso to tune a logistic regression model

I am trying to make a logistic regression model using the lasso technique. I have 56 potential predictor variables (IVs), and I would like to use lasso to select a parsimonious set of predictors. The ...
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### Generating Skewed Z-Scores with Kurtosis

I am looking to programmatically generate random z-scores from a distribution with a specific skew and kurtosis. Can anyone provide a mathematical technique or code (VBA or C++ preferred but I'll take ...
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### Correlation analysis among large number of variables

How can I check correlation among large number of variables? I can check the scatter plot between every pair of variables and pearson coefficient r if the number is ...
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### Time series analysis: since volatility depends on time, why returns are stationary?

I run Dickey Fuller test in order to know if stock returns are stationary. I get that no matter which stock I take, his return is stationary. I don't know why I get this result since it is clear that ...
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### Using Mann-Whitney U instead of T-test in large sample

For my dissertation, I am examining racial differences in perceived choice and control and home and community-based services (HCBS) use in frail elders (n=659) who have moved from a nursing home into ...
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### Best Measures for face detection

I'm trying to evaluate series of face detection algorithm. For that I need the best protocol or measures to distinguish each algorithm. As output I only have the number of faces detected (until ...
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### How to generate n theano.shared variables for Gaussian mixture regression?

I am trying to program a Gaussian mixture regression using python, and the theano package. Suppose I have n clusters, then I need to generate n regression weight matrices for each cluster (also, n ...
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### What is the mathematically rigorous definition of chunky data?

When in the workplace, certain measurement-taking devices are subject to different numerical accuracy; in some cases, the accuracy can be pretty weak (i.e., to one or two significant values only). ...
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### Can I be confident of my R^2 score?

I have a dataset with 10 variables and 158 observations. I used cross-validation, grid-search and ElasticNet algorithm. To evaluate the model I checked the pearson correlation between the 10 ...
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### Is Propensity Score Matching the Correct Tool to Match Cohorts by Disease and not Exposure?

For a set of patients that all underwent procedure A, is it valid to use propensity score matching to compare 2 subsets in which the patients have disease D (D+) to those that do not have disease D ...
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### What is the variance of a normally distributed random variable minus the sample mean of the data it came from?

If $Y_i \sim N(\beta, \sigma^2), i = 1,2,\ldots,n$ and $U_i = Y_i - \bar{Y}$, then what is the distribution of $U_i$? I know that $\bar{Y} \sim N(\beta, \sigma^2/n)$ and that the sum (or difference) ...
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### R & propensity matching [on hold]

I am new to R & propensity matching. I doing a quasi-experimental study in which a group of 320 students received treatment and a group of 280 students did not receive treatment. I would like ...
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### Power Analysis for Within Subject ANOVA

I am going to be collecting survey data that asks for participants' attitudes towards four groups of people. For the sake of this example, let's say that it's black women, black men, white women, and ...
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### How to use interpolation to calibrate object distance measurement based on pixels?

The current method used is triangle similarity to find the distance. A test image was used with known distance and known width. Then the area of the object in the image can be calculated. The ...
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### add legend to ggplot geom points [on hold]

I've created a ggplot indicating 3 different activities for male bats in three different colours: ...