# All Questions

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### Shrinkage the Sample Covariance matrix

Assume we have N independent and identically distributed random vectors $X_1, X_2, ..., X_N$ where each of them is of size p $\times$ 1. The sample covariance matrix, denoted here by $S$, is computed ...
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### Difference scores in linear mixed models?

I have a question about how to interpret fixed effect interaction coefficients, which appear to be difference scores, in linear mixed models using SPSS. I am looking at the consistency of ...
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### Calculate Var(X/Y) for dependent variables?

I understand that you can calculate Var(X*Y) through Bienayme, whether variables are dependent or not. I am wondering if there is a similar way of calculating Var(X/Y) when variables are dependent? ...
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### Why are Hinton's multilayer deep-learning networks stochastic?

Firts I'll sum up my intuitive (beginner) understaning of his deep-learning architecture. A short summary can be listened to on Coursera in the 5 minute video. We start with several layers of ...
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### What can be deduced from the variance and cramer rao bound?

I have computed the cramer rao bound of the estimates of the coefficients $\mathbf{h^T}$ for a moving average model (MA) involving 2 different process noise : (1) when the process noise is a random ...
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### Relationship: Regression Coeffecient and Line Plot Trendline Slope

Why does the slope of my line fit plot not match the coefficient of the same variable in my regression? For one of the variables, the coefficient is positive while the line fit plots trendline is ...
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### MLR, should all interactions be included even when irrelevant for tested hypothesis?

I have two simple questions yet I could not find a direct answer to either of them, so I would be thankful to anyone who could help me. I have 3 independent variables, X, Z and Q, where X is ...
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### sample size of infinite population and alternative comparisson

I need to compare two alternative methods of manufacturing a product, say A and B. I wanted first to dermine the sample size of ...
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### Do I need to categorize likert responses so I can use logistic regression?

I'm conducting a research project to evaluate burnout level among critical care nurses and whether this level can be related to other variables (age, workload, unit, etc). Burnout level is measured ...
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### How to compare (probability) predictive ability of models developed from logistic regression?

I know some well-known measures are $c$ statistic, Kolmogorov-Smirnov $D$ statistic. However, as far as I know, those statistics take into account only of the rank order of the observations, and is ...
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### How do I use weight vector of SVM and logistic regression for feature importance?

I have trained a SVM and logistic regression classifier on my dataset for binary classification. Both classifier provide a weight vector which is of the size of the number of features. I can use this ...
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### Marketing analytics texts

Can you recommend a comprehensive textbook or a monograph on marketing analytics? I'm interested in metrics, measures and statistical methods used in the field. For instance, what are the approaches ...
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### Coding factors with non-numeric settings

For my role as a TA I am assisting the instructor in developing curriculum based on DOE and statistics. We have a set of failure strengths (the output/dependent variable) for several glass rods. The ...
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### FONT Problem: SAS Enterprise guide 6.1 on Windows 10 [on hold]

Today, I installed Windows 10 on my new computer. Then I installed SAS 9.4 M1, included SAS Enterprise guide 6.1M1. However, the program window's font in SAS Enterprise guide looks awkward. Fonts ...
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### How to separate “rates” with TukeyHSD?

My data is formated as Treatment and Cultivar, which are factors, and GDD, which is a continuous variable. The response variable is DTA_R, so my model is basically glm(DTA_R~TreatmentCultivarGDD). I'm ...
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### Multivariate Regression Analysis in SPSS

I am using SPSS to perform a multivariate regression analysis. I have 4 factors, Group (1,2), AgeGroup (1,2), Sex (0,1), and handedness (0.1) with 4 dependent variables. My question relates to ...
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### How does one call external datasets into scikit-learn? [migrated]

For example consider this dataset : (1) https://archive.ics.uci.edu/ml/machine-learning-databases/annealing/anneal.data or (2) http://data.worldbank.org/topic How does one call such external ...
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### Encode special values in continous predictors

I have continuous variable with missing values. Missing values are of different types (indicated by special values such as 991, 992). How do I best encode my data for logistic regression? I can create ...
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### Cohens d effect sizes

I'm using Cohens d effect sizes as a means of providing a magnitude based inference in a study I'm conducting. I just wanted to clarify if I'm correct here: Anything between .0 and .2 is small. ...
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### How does Shuffled-Complex-Evolution-Metropolis algorithm compare to other adaptive samplers (e.g. NUTS)?

I recently heard of the Shuffled-Complex-Evolution-Metropolis algorithm and am curious how it compares to other adaptive MCMC sampling algorithms. Unfortunately I am still learning about optimizing ...
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### How to deal with the different outcomes between pairwise correlation and multiple regression

I have different results from a correlation table and a multiple regression model. I know that it is an effect of multicollinearity because correlations up to $.474$ exist between predictors, but this ...
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### Family-wise error boundary: Does re-using data sets on different studies of independent questions lead to multiple testing problems?

If a team of researchers perform multiple (hypothesis) tests on a given data set, there is a volume of literature asserting that they should use some form of correction for multiple testing ...
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### Hiding the 0 pixel values from the image in display [on hold]

i have a binary image and don't want to show the 0 pixels values in display, so i can superimpose it into an other image how i can do that ? I change the transparency of the image but its for the ...
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### Natural Resource Management: How do I estimate the odds ratio and confidence intervals from model-averaged estimates?

I'm currently working on a model selection analysis in the field of natural resource management. My research question is: what variables are important to an avian species nest site selection. My ...
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### How to interpret the numeric values for “height” using wards clustering method

I am a biology student investigating a new method of creating a dichotomous identification key. I have created a dendrogram using data I have collected from a survey on how people rate how similar ...
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### How to specify a multi-instrument 2SLS

I'm looking for a compact way to specify a multi-instrument 2SLS in R. Imagine that there are four treatment categories (A, B, C, and D). There are two waves of measurement, Y_1 and Y_2. A ...
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### Autocorrelated Extreme Events

I'm using a bunch of techniques and methods from Extreme Value Theory to analyze my data. I have a time series representing the number of events happening in a given day. The time series is unequally ...
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### Ranking Data through rank number

Suppose in my survey, through one question, 100 respondents are asked to rank all the 5 product-attribute options for buying a product by giving separate rank numbers (from 1 to 5) to each of 5 ...
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### Predict number of users

I have a pretty basic question, but am pretty far removed from stats and modeling. I have historical data (daily, weekly, monthly, however I want to slice) for a few years and I want to predict the ...
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### The Shepard function in R package MASS

The function Shepard is listed in the help file for MASS::isoMDS, but nothing is said about it. What does this function do?
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### How to analyse the accuracy and standard deviation of a neural network in matlab toolbox?

I am new in Matlab and neural network, and I am doing a prediction with some data that I found on the internet to learn more about it. Here is my function to create a neural network: ...
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### What is the best way to analyse data comparing one by one and stipulate the accuracy?

Follow the example: The first line is the data I got. The second line is the target data. | 154.0 | 784.4 | 854.1 | 789.3 | | 153.5 | 789.7 | 892.3 | 903.2 | I ...
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### Is large scale PCA even possible?

The PCA algorithm assumes that the input matrix columns are with mean zero. This can be achieved easily, but when the input matrix is sparse, the centered matrix will now longer be sparse, and will ...
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### Closed form of conditional probability for a specific joint

I have a joint probability of a very specific form: $P(x_1,\cdots,x_n)=\phi(x_1)\psi(x_1,x_2)\phi(x_2)\cdots\psi(x_{n-1},x_n)\phi(x_n)=\prod_{i=1}^n \phi(x_i) \prod_{i=1}^{n-1} \psi(x_i,x_{i+1})$ I ...
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### What is the formal definition for $\sim$ in the context of statistics?

If $X\sim N(\mu,\sigma^{2})$, we say that $X$ follows a normal distribution with mean $\mu$ and variance $\sigma$. How is the operator $\sim$ formally defined?
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### Cramer Von Mises - How to use this test correctly?

I had a problem when I tried to test the fitting of my data with the generalized Pareto distribution. I used the MLE to estimate the two parameters 'shape' and 'scale' and I generated a vector of ...
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### How to Find the Correlation in Time Series of Categorical Variables in R?

I have a data set of categorical variables occurring weekly. A sample dataset can be found in my previous post. I want to check the co-existence of these categorical variables over time. I want to ...
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### Statistic to use to measure intersection probability in set of elements

Being two sets of elements: set a: ele1, ele2, ele3, ele4, ele5, ele6, ele7 set b: ele3, ele4, ele8, ele9 And is intersection: ...
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### What are some tests for the predictability of time-series?

I have 2500 time series which I want to test the predictability and based on that, choose the best one to forecast. Ideally I want to use a simple model like ARMA-GARCH for forecasting. Are there ...
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### Modeling rent share as a function of income [on hold]

I want to model the share of income spent on rent as a function of income and a few other variables. Now the dependent and explanatory variables are not dependent. Is this a problem.? Or is it ...
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### Help: Text Mining + Classification - From customer comments to predicted solution [on hold]

I have a data set that consists of the information generated by a service call for a home appliance. The data set consists of a column with the sentence of the customer's complaint and a ...
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### Are this two definitions of survival equivalent

Let $\lambda_i(t)$ denote hazard of the $i$-th individual at time $t$ and let $\lambda(t)=\frac{\sum_{i=1}^n S_i(t) \lambda_i(t)}{\sum_{i=1}^n S_i(t)}$ be the weighted average of individual hazards. ...
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### Multi-step ahead forecasting with Weighted Moving Average?

The Weighted Moving Average method is usually used for smoothing purposes. However, it can be used to forecast $Y(t+1)$ based on the last n observed data. In real-world problems, forecasting in very ...
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### How to extract interaction pairs from glinternet object? [on hold]

I am using the first time glinternet and wonder how I can extract the selected/important interactions from it. I use the following code: ...
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### understanding accuracy assessment of classification

I want to classify an image and I want to know how well I did, but I am not sure if I understand the workflow properly. I use scikit-learn. I first use cross_validate and GridSearchCV to find the ...
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### What are some ways to normalize variables to compare standard deviations?

I have a list of time-series variables which are all in different scales. The variables are not normally distributed and some values are negative. What are some ways to normalize these variables so ...
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### Non-independent variables (covariates) in survival analysis

I want to perform survival analysis, and compare at which of 3 spatial scales habitat variables affect the most nest survival. I thought to perform analysis separately for each spatial scale and ...
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### Interesting Logistic Regression Idea - Problem: Data not currently in 0/1 form. Any solutions?

I am attempting to conduct a logistic regression for a tennis analytics project, endeavoring to predict the probability of a player winning a point in which he is the server. My response variable ...