# All Questions

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### spss principal axis factoring output problem

I am trying to run a factor analysis (SPSS) using principal axis factoring with an oblique (or promax) rotation because the variables are highly correlated. However, the output for "total variance ...
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### Question regarding parameters and variable selection in Mahout algorithm for logistic regression

Below is the list of parameters in Mahout logistic regression. What does "passes" mean? In detail please --passes passes the number of times to pass over the input data ...
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### Calculating distances between centroids in an Primer 6 MDS plot

I am just wondering if there is a way to calculate the distances between the centroids generated by Primer 6 in a MDS plot. I am trying to find if the centroid distances change beween samples but I ...
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### Experiment design

We have x1 and x2 representing variations in temperature and pressure and the response is yield of penicillin. What is the practical reason for using the points (-1,-1), (-1,1), (1,-1), (1,1) rather ...
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### simulate dirichlet process in R

I am reading the paper of Dirichlet Process Mixtures of Generalized Linear Models authored by L. A. Hannah. If I would like to simulate the following model In R, ...
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### Decision Level Fusion of SVR outputs

I have two sets of features predicting the same outputs. But instead of training everything at once, I would like to train them separately and fuse the decisions. In SVM classification, we can take ...
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### Residual plot for regression tree: What should it look like?

I realize that decision trees are nonparametric methods What should residual vs. actual/fitted look like for a well behaved regression tree? My argument would be that since each observation assigned ...
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### Hypothesis test on a series of wagers with different probabilities and returns

I have a model that predicts the probability of an event occurring, and then based on a given return if the event occurs, calculates the expected value. If the expected value is positive, a wager is ...
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### statistical comparison of power spectrums over all frequencies

So I have N=147 control time-series signals and N=134 treatment (THC) signals. I want to compare if there are any significant differences in frequency power in the two groups. The top part of the ...
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### Why does eigenvalue decomposition of a correlation matrix maximizes possible variance?

I was reading up on principal component analysis and I was wondering how does eigenvalue decomposition of the correlation matrix maxmimizes the possible variance that is captured? Can someone refer to ...
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### Possible problem for Network Analysis

I have a data set and I want to examine an hypothesis in there and probably Network Analysis should prove or reject my theory. I have a list of products and a group of people who give the product to ...
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### Deep belief nets and PCA

I have been using successfully DBNs for classification for MNIST and some other tasks. I was thinking of doing dimensionality reduction before training, in order to boost performance. However, when I ...
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### Is my dataset suitable for a mixed effects model?

I've been putting a lot of work over the last few days into bring mixed effects models to bear on some behavioural data I've collected for my thesis, but it's occurred to me that I'm not 100% sure ...
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### Increasing power of test by transforming format of data - is this cheating?

I'm working on a health care dataset that contains one row per member, measuring total number of the member's hospital inpatient (IP) visits during 2012 and 2013. The initial research question of the ...
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### Tolerance for pseudoinverse

In calculating the pseudoinverse of a matrix $A$, of size (m,n), I need to choose a tolerance threshold for the eigenvalues. I'm trying to understand how I should pick this. Matlab default is to use ...
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### R latent class multinomial logit model

I am using the flexmix package to estimate latent class multinomial logit models in R. In choice theory, there can be variables associated with the alternative ...
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### R: result of Levene test correct?

I want to use the Levene test to quantify the homo/heterogeneity of the variances of two samples. The density plot looks like this: But the Levene test for the data [...
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### Linear correlation in ANCOVA - necessary?

I've been told by my stats prof that running an ANCOVA relies on a series of assumptions, including that the the dependent variable and the covariate are linearly related. So, in SPSS the first thing ...