# All Questions

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### Adjusting for a mediator to capture cross sectional relationship

We are fitting a linear model using cross-sectional data to inspect the relationship between some exposure and an outcome (disease status, measured continuously). Duration of disease was also captured ...
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### Expectation of ratio of functions of Bernoullis: a concentration question

Consider the following $n \times n$ symmetric matrix of i.i.d. Bernoulli random variables, $X_{ij}$. For $i=1,...,n$ and $i<j\le n$. Let $X_{ij} \sim \text{Bernoulli}(p)$ when $i \ne j$, and let ...
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### Good sources to get papers in machine learning?

I'm a CS master student (will be a PhD in three months or so). Today I was at my superviser's office and he had a friend discussing some ideas for their research. Then they mentioned a paper that I ...
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### GEE with exchangeable working covariance vs. GLM and using Clustered Robust standard errors?

I'm analysing a dataset including 100 individuals. These 100 individuals provided self-reported depression sores on equally spaced 4 occasions (every three months). The main independent outcome is ...
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### How to test main effects of categorical variables in a binary logistic regression including an interaction?

I measure two binary responses from each participant (ChoiceVA = V or A, AestheticOnly = 0 or 1). There are two experiments (between-participant). I want to test the following hypotheses: ...
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### Calculate at .05 level of significance

A research organization claims that the monthly wages of industrial workers in district X exceed those in district Y by more than Rs 150. Two different samples drawn independently from the two ...
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### Use Taxometric analysis in addiction disorder

I'm just to start my research dessertation and bring topic about taxometric analysis. However i'm heading trouble about the concern in it. Lets say when use taxometric analysis, it mean we face all ...
9 views

### How can I work out the standard deviation of a t-distribution?

Given a t-distribution with a certain df, how can I work out what the SD of that distribution is?
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### how to perform intensity-based similarity metrics on two images rigidly transformed on matlab?

i got two MRI images on matlab, i need to perform an intensity based registration similarity metrics in order to get a registration. The problem is that, since i got some rigid transformation on one ...
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### Weight Decay in Neural Neural Networks Weight Update and Convergence

I have a neural network (That I created using java) for a class assignment that is working when I do not use any weight decay value, but when I use a value greater than or equal to .001, my accuracy ...
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### Estimating necessary sample size

I am pretty new to statistics and I'd like to get pointers on the correct way to do this. I have a dataset in which I'm interested in the 50th and 90th percentile. I'd like to take a sample of that ...
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### Wold Representation for an ARMA (1,1)

I have this ARMA(1,1) process where $\epsilon_t$ is the classical White Noise process$$X_t=\epsilon_t +\alpha_{t-1}\epsilon_{t-1}+\theta_{t-1}X_t$$ and I have to write its Wold representation. Using ...
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### The likelihood that a time series is generated by certain ARMA(p,q) ?

I have a group ( only 20 of them, each one has 170 time pointers) of time series that I can consider as "GOOD", meaning, they have consistent statistical characteristics. I am not sure how they are ...
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### In R: Replace values of a row if missing with values of another row [migrated]

I am relatively new to R and probably the solution to this problem is rather simple. I have a dataframe that looks like this: ...
17 views

### Number of trials to observe all values of a uniform discrete random variable X with a probability of at least 1-q?

Let X take on p values with equal probability. If n trials are to be conducted to ensure that the probability of not observing any of these p values is less than or equal to q, what is the value of ...
19 views

### Using third validation set in Cross Validation?

(Note there's 2 paragraphs of background information before I get to the question) I've got a Neural Network classifier, trained with an EA to classify data. I previously used a holdout framework ...
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### How to classify test objects?

I'm coding a program that tests several classifiers over a database weather.arff, I found rules below, I want classify test objects. I do not understand how the classification, it is described: "In ...
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### How can I optimize coefficients of an arbitrary model?

This might be terribly easy but I'm probably lacking the keywords to search for. Assume the following (dummy) data: ...
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### Is there an article/book reviewing different methods for constructing posterior point/interval estimates?

Given a one-dimensional posterior distribution it is often the case that you want to calculate a point estimate and a credible interval for the corresponding parameter. There are, of course, many ways ...
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### How to use k-fold cross validation in naive bayes classifier?

I'm trying to classify text using naive bayes classifier, and also want to use k-fold cross validation to validate the result of classification. But I'm still confused how to use the k-fold cross ...
14 views

### lmer with multiply imputed data

How can I get pooled random effects for lmer after multiple imputation? I am using mice to multiple impute a dataframe. And lme4 for a mixed model with random intercept and random slope. Pooling lmer ...
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### Logistic regression: Is it legitimate to exclude a main effect (part of interaction term) when predicting new values? [duplicate]

I have two main effects and an interaction term. The interaction (IsolateTemperature) term and one of the main effects (Isolate) is significant. The other main effect (Temperature) is not. I want to ...
22 views

### Why is my probability incorrect?

There is a building with 7 floors and 8 apartments per floor. The building has 2 vacant apartments. A lady wants an apartment on the top floor. What's the probability that she finds one in this ...
15 views

### Which measure of Central Tendency should I choose for skewed data?

I am trying to find out the best measure of central tendency from a list of data. As a first step, I'm trying to figure out the outliers in my distribution by using the usual Q1,Q3 and IQR formulas. ...
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### Two repeated measures treatment analysis. Regression of the delta or mixed effect model?

We want to study the effect of a certain treatment on performance on a test and I would like to have some suggestion from you. We want to use a regression model in order to control for confounders. ...
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### model post-event misinformation effect on eyewitness?

I'm trying to model post event misinformation. The questions i have is the factors affecting it. and a psychological way of assessing it.
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### Logistic-Regression: Prior correction at test time

Using sklean.linear_model.LogisticRegression for a binary classification problem. My classes are unbalanced. The positive class comprises about 20% of the training set. When fitting the model I use: ...
14 views

### Multivariate Statistics

How to plot an ellipse from eigenvalues and eigenvectors for [ 5 4 4 5]. I know eigenvalues are 9 and 1 and eigenvectors are (0.5,0.5) ...
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### In ensemble predictions, what is reliability diagram?

I have recently heard the term reliability diagram used with regards to the analysis of ensemble predictions. What does it show and how is it calculated?
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### Multilevel analysis. Between hospitals variance

Please help me with the multilevel analysis. Certain medical procedure is performed/not performed in hospitalized patients. The % of patients that receive this procedure varies across different ...
17 views

### Crossover and Mutation in Genetic Algorithm

I am studying how GA works. It is known that GA obtains the optimal solution by iteration through the the process of reproduction, crossover, and mutation. When crossover and mutation, the ...
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### Discovering dis-associations between periods of time-series

I'm interested in discovering some kind of dis-associations between the periods of a time series based on its data e.g. find some (unknown number of) periods where the data is not similar with the ...
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### How to define my custom cost function to be used in (stochastic) gradient descent?

I have a text classification problem were the classes are 20 cities and the input is text Bag of word features. I am using Logistic Regression and my cost function is negative log likelihood: ...
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### How is RKHS useful in prediction tasks

Before reading about Hilbert spaces I am trying to get an intuition of how they are useful in prediction tasks. Is it as follows - Suppose we are performing a prediction task trying to approximate Y ...
30 views

### Density distribution of outcomes of 2 dice rolled [duplicate]

This question is related to: http://stackoverflow.com/questions/26153925/r-studio-a-histogram-with-a-bar-for-each-frequency-value Amongst the outcomes of 2 dice rolled, the chances of 2 are equal to ...
27 views

### How does simple linear regression minimize least squares [on hold]

Intuitively, how does simple linear regression minimize the squared residuals?
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### Check homogeneity of variance for linear mixed model in spss

I ran a linear mixed model (LMM) for my nested data and would like to check for the homogeneity of variance assumption. As there is no a button for checking the homogeneity of variance at the LMM ...
12 views

### What does O(t) correction mean?

I was reading a journal article and it mentioned an "O(tau) correction" THe "O" was actually more like a script "O". I am sorry I cannot find the symbol in Word of Excel. PLease let me know what it ...
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### How to prevent line to extend across whole graph [migrated]

Currently, the below code (part of a more comprehensive code) generates a line that ranges from the very left to the very right of the graph. ...
15 views

### Interpreting the value of standard errors [duplicate]

After computing the standard error of regression, my answer is 3.55 what does the value mean
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### How to not only compute predicted values but also standard errors [migrated]

I am trying to generate standard errors for predicted values. I do manage to generate the predicted values, however, do not get the standard errors. Instead, I consistently get the following error ...
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### Random Forest - Huge Disparity between OOB Error and test data error

I am building my model in R and am using the randomForest package. My current model has 7 features and I see OOB error rate of about 14%. I also ran the rfcv in the random forest package to see how ...
13 views

### Wilcoxon Rank Test or T-Test? [duplicate]

What data analysis is better? or fit for my data? I've used Likert scale for my questionnaire (1-5) and I have 387 respondents. Wilcoxon Rank Test or T-Test?
11 views

### Understanding Gaussian Basis function parameters to be used in linear regression

I'd like to apply the Gaussian basis function into a linear regression implementation. Unfortunately I'm having a hard time understanding a couple parameters in the basis function. Specifically mu ...
17 views

### Two step cluster analysis and a binary matching coefficient

I want to commence a two-step cluster analysis, since the database I am conducting analysis on contains important metric as well as nominal values. => Question #1: Should the binary and the metric ...
20 views

### How to estimate a Logistic Regression function in a quadratic form?

I am trying to use a mixed-integer programming solver to optimize the following logistic regression function: $$\mathop {\min }\limits_w {{\exp ({w^T}x + b)} \over {1 + \exp ({w^T}x + b)}}$$ There ...
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### Can a Likert scale be analyzed with parametric statistics? [duplicate]

I'm working with data collected from a psychometric instrument (96 questions) with a Likert-type response format (5 choices). For the data analysis, I'm following a methodology that implyes t tests ...
17 views

### Back transformation with power function

I have the following distribution, where each observation represents a metric. $Metric = \frac{NExplored Nodes \times NGenerated Nodes}{NRepeated Nodes}$ This metric is highly correlated (0.99637) ...